Hi passat,
You can see my thoughts about Northwest Bedding in post #10 here and a forum search on Northwest Bedding will bring up more information and feedback about them as well.
While they would generally be a better quality/value choice than most mainstream mattresses or major brands … outside of testing a mattress for PPP (Posture and alignment, Pressure relief, and Personal preferences) using the testing guidelines in the tutorial post (which is the most important part of a mattress purchase) … a mattress is only as good as its construction and the quality of the materials inside it regardless of the manufacturer so I would make sure that you know the specifics of any mattress you are seriously considering (see this article) so that you can make meaningful comparisons with other similar mattresses.
I’m certainly happy to help with “how” to choose but there are too many unknowns, variables, and personal preferences involved for anyone to suggest “what” specific mattress to choose for someone else based on “theory at a distance” (see mattress firmness/comfort levels in post #2 here).
The brand of a mattress is also not particularly important (outside of whether they will disclose the information you need to evaluate a mattress) because outside of testing for PPP … the quality of the materials are always more important than the name of the manufacturer on a label and all manufacturers have access to similar materials that they can use inside their mattresses.
Phoenix