Hi hassiman,
I switched your post into a new topic of it’s own so our conversation wouldn’t get mixed in with a different topic.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses.
You can see my comments about Bedinabox in post #2 here. I would be very cautious with any mattress that uses 3 lb memory foam which is a lower quality and less durable material and I would consider this to be a weak link in their mattresses.
Novosbed is one of the better quality/value online memory foam providers I’m aware of (which is why they are included in the online memory foam list here) and Aria and Harmony both use good quality materials and there are no lower quality/density materials or obvious weak links in either of them.
The Aria is designed to be closely comparable to the Tempurpedic Cloud Supreme and the Harmony is designed to be closely comparable to the Sealy Optimum Elation Gold so you can test both of these mattresses locally to get a better sense of how each of them will feel and perform for you and of course Novosbed will also be able to provide you with good guidance on the phone as well.
NOTE ADDED JAN, 2016: They have now introduced their new simplified choice mattress which has replaced their previous models and have also become a member of this site.
A forum search on Novosbed Aria and on Novosbed harmony (you can just click the links) will bring up all the forum posts that mention both of them but I would be very cautious about using other people’s experiences on a mattress (either positive or negative) as a reliable source of information or guidance about how suitable a mattress or any specific material may be for you and in many cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person may be completely unsuitable for someone else to sleep on (see post #13 here).
Hopefully you’ve also had the chance to read the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice.
Phoenix