Hi ima,
Now that’s funny … and I’ll happily take the blame for this one 
My own thoughts about the different “directions” in buying a mattress would go something like this …
OPTION 1: My first choice would be to buy something I know and had tested locally. This would be particularly true if it involved a knowledgeable and experienced local manufacturer or retailer that was transparent about the type and quality of all the materials and components in their mattresses (so I knew the quality and value of what was in my mattress) and who would be able to provide some good guidance and/or has good options and/or suggestions after a purchase to help you make any “fine tuning adjustments” at a nominal cost if my sleeping experience didn’t quite match my testing. This is by far the least “risky” option and well worth a premium over other approaches IMO.
OPTION 2: If there were no high quality and value local options, or if the difference between what I wanted to buy locally was more than about 20% (as an arbitrary number that each person can decide for themselves) compared to a directly comparable mattress from an online manufacturer or retailer … then I would consider going in the direction of buying online with the help and guidance of a manufacturer or retailer who has the experience and knowledge to help you make your best choice out of the options that they offer. They often offer choices that can help you customize your mattress to different degrees and/or usually offer some ability to change your choices after a purchase at a reasonable cost if it doesn’t turn out quite right. While this is more “risky” because sometimes smaller changes from your “preferred” design can make a bigger difference than people suspect, this risk can be reduced with more detailed conversations with the manufacturer who you are considering. Sometimes the opposite is also true that some differences will be less important than someone who analyzes too much may think. If the price difference and your “personal value equation” justifies it though, it would certainly be worth strong consideration.
OPTION 3: The final direction is the riskiest of all and involves buying separate components from different places where you may not really know how the layers and components you are buying will interact together. I would consider this direction if the potential savings over option #2 seemed significant enough to make the added risk worth it. This approach involves more knowledge and preferably some detailed local testing of known layers to reduce the risk and cost of making mistakes which can add to costs. If you have the knowledge of materials and enough experience from local testing to be able to predict with some certainty which layering will be best for you then it can be the least costly of all the options (although it sometimes doesn’t represent significant savings over option #2) but if you lack the knowledge or experience you need then this can also turn into a “project” with unexpected difficulties or surprising results. If you end up with “components” that aren’t quite right … there can be a much greater than expected cost involved in buying new layers and making adjustments after the fact.
It can be very satisfying to build your own mattress but I would only go in this direction if your knowledge level and personal experience with different types of foams, mattress components, and layering combinations was well above average and in full awareness of the possible risks and additional expenses involved in the trial and error process. I would also try to stick with proven designs and use the same materials, layers, and construction as much as possible (including the cover which is often overlooked and can have a significant effect on the feel and performance as well as the cost of the mattress). This method is more about becoming an expert rather than the simpler method of “finding the experts” either locally or online. In effect you are exchanging a great deal of time, effort, study, research, local testing, a steep learning curve, and the possibility of some costly mistakes for the potential of some savings and of course on the other side the satisfaction that can come from designing and building a mattress completely on your own. Post #15 here and post #5 here and post #7 here and post #25 here would also be worth reading if you decide to go in this direction
The “best” approach to a complete DIY mattress is a “spirit of adventure” and a willingness to go through the trial and error it can involve and where what you learn and the satisfaction that comes from the DIY process itself is more important than any cost savings you may realize (which may or may not turn out to be the case).
In your case … a 2" layer of N25 Dunlop over a 1" layer of N36 Dunlop would be fairly similar to what you tried and liked but there would be a difference because of the different materials that were underneath it. This would be on the firm side for a typical side sleeper (although heavier weights would feel this as softer than lighter weights and you have the advantage of having tried this and knowing that it provided enough pressure relief on your side) but the advantage would be that it would be better for stomach sleeping because there would be less of a chance for sleeping in a swayback position. Bear in mind too that the type of quilting/ticking used would also play a role in how any particular option felt to you.
So overall you are going in a good direction in terms of what you are considering IMO. You are asking the “right” questions. In essence you started with #1, are considering #2 and considering moving towards #3. The goal is to make your choices with realistic expectations of success.
If you decide to go all the way into #3 … then choosing layers that have known specs and that closely approximate what you have tried in person and worked well for you can be a good blueprint. In this case … I would check the websites and/or call and talk with the online manufacturers of this site as a “reference point” in terms of cost (DIY Natural Bedding, SleepEz and Arizona Premium / mattresses.net offer layers as components and often carry layers which are not listed on their site) and then purchase the components from a reliable source that describes their products accurately and that you have confidence would actually supply what you are ordering. Post #4 here has a list of sources for various mattress components for those who are going in the direction of option 3.
Foam Order would be a supplier that I would consider to be good although they may not always have the best prices when compared with other options. Amazon, Overstock, and other even “riskier” choices like Ebay could also be good choices for materials and components if you have confidence that what you are buying is correctly described (which is not always the case) and suitable for your needs and preferences. This can take some research.
Zip covers of various types (quilted with wool or other materials and unquilted) can be also purchased from one of the sources listed in the DIY link two paragraphs up. Making sure the cover you buy fits well with the layers you are buying is also important. You want a nice tight fit not a loose “approximate” fit or one where you have to squish the foam too much to get it in (which will change the feel of your mattress).
So overall … I would take a careful look at the benefits and cost savings of each approach and compare it with the realistic risk … plug this into your “personal value equation”… and then go in the direction that you are most comfortable with and lets you be the involved in the design and construction of your mattress to the degree that you feel best about.
Phoenix