Hi Ljj,
Welcome to the Mattress Forum! 
Hah – yes! :lol: With the price of some mattresses these days, you would expect to be able to drive them back and forth to work.
The major brands such as Sealy/Stearns & Foster, Simmons, and Serta all tend to use lower quality and less durable materials in their mattresses than most of their smaller competitors that will tend to soften or break down prematurely relative to the price you pay, which is why I would generally suggest avoiding all of them completely (along with the major retailers that focus on them as well) regardless of how they may feel in a showroom along with any mattress where you aren’t able to find out the type and quality/durability of the materials inside it (see the guidelines here along with post #3 here and post #12 here and post #404 here).
Tempurpedic mattresses use good quality materials, but as you stated they are in much higher (and mostly unjustifiable) budget ranges and for most people they certainly wouldn’t be in the best “value” range compared to many other smaller manufacturers that use similar (or in some cases better) quality materials that are in much lower budget ranges. You can read more about Tempurpedic in general in posts #1 and #2 here.
The Tuft & Needle is one of the earlier “simplified choice” mattresses, and it is made entirely of polyfoam, with a 7" 1.8 lb polyfoam core under a 3" 2.8 lb polyfoam comfort layer. For most people there would be no “weak links” in the mattress, but I would provide a slight caution for those like you who are in the mid 200’s or higher, as the 1.8 lb density base layer can reduce the useful life of the mattress for someone with your mass. You can perform a forum search on Tuft & Needle here, and there is a bit more about them in the simplified choice thread here.
While other people’s comments about the knowledge and service of a particular business can certainly be very helpful, I would always keep in mind that you are the only one that can feel what you feel on a mattress and I would be cautious about using anyone else’s suggestions, experiences or reviews on a specific mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you. In many, if not most cases, they can be more misleading than helpful because a mattress that would be a perfect choice for one person or even a larger group of people in terms of comfort, firmness, and PPP may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range). In other words, reviews or other people’s experiences in general won’t tell you much if anything about the suitability, quality, durability, or “value” of a mattress for any particular person (see post #13 here).
You can also see my comments about the Consumer Reports mattress ratings and recommendations in post #2 here and in this topic. While they may be a good source of information about more “objective” purchases … as you can see I would consider them to be an unreliable source of information or guidance about purchasing a mattress and their “ratings” are somewhat nonsensical and meaningless. My thoughts are also shared by most of the more knowledgeable people in the industry (see post #5 here for an example).
Most mattresses these days are made to be “adjustable bed friendly”, with latex being the most flexible, followed by memory foam and polyfoam mattresses, and then many of the “newer” innerspring mattresses (most often pocketed spring units) made to contour along with a power foundation. “Zero Gravity” is trade name to describe the semi-Fowler’s position (knees at about 135 degrees and hips at about 45 degrees), taking the stress off of the hip flexors and decreasing the lumbar lordosis slightly, and can be accomplished by any adjustable bed base unit having separate motors adjusting the head and foot section.
This is the memory foam offering from Saatva. They use a 5.5" 1.5 lb polyfoam core, on top of which is a 2" 1.5 lb piece of poly foam, then a 2.5" piece of 5 lb memory foam that is topped with a 2" piece of 4 lb convoluted memory foam. Saatva wouldn’t disclose to me the density of the bottom two layers (see post #2 here ) so I recommend to treat them both as 1.5 lb density. I would be cautious for those that are in higher weight ranges (more than the low 200’s or so) or perhaps even a little lower than this because of the lower density polyfoam layers and the 4 lb convoluted gel memory foam in the top layers. You can perform a forum search on Saatva and Loom & Leaf here, and there is a bit more about them in the simplified choice thread here.
If you haven’t already, I would refer to the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
If you have more specific questions, I’ll be happy to do my best to be assistive.
Phoenix