Hi pthalo,
There are too many unknowns, variables, and personal preferences involved in a mattress purchase for anyone to recommend a specific mattress or brand for someone else based on specs (either yours or a mattress) or “theory at a distance” because a mattress that works well for one person may be completely unsuitable for someone else to sleep on regardless of the quality of the materials or the price of the mattress (see mattress firmness/comfort levels in post #2 here). Since I can’t feel what you feel or see you on a mattress I don’t recommend specific mattresses or brands and focus on the information and steps in the tutorial that can help with “how” to choose rather than “what” to choose (see post #5 here).
Having said that … I do recommend dealing with smaller manufacturers that are sold factory direct or through better retailers across the country who are transparent about the materials in their mattresses and have the knowledge and experience to be able to help you make better choices and meaningful comparisons rather than just “selling you” anything they can. The manufacturers and retailers that have been invited to become members of this site all compete well with the best in the industry and I would certainly recommend including them among your options if they are close enough to to visit or if you are considering an online purchase (for the ones that sell online and ship their mattresses across the country).
Once you get to step 3 in the tutorial I’d also be happy to let you know of any of the better options or possibilities I’m aware of in your area whether they are members here or not.
Low back pain is generally an indicator of a mattress that is too soft for you (and has little to do with the quality of the mattress). The mattress testing guidelines that are linked in the tutorial post (in step 4) can also help you choose a mattress that would be more suitable for your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
Phoenix