Hi jp191 and welcome to the Mattress Underground 
I’m a 6 foot 2 man, about 240 lbs, mid-30s, living in Los Angeles, and I’m looking for a new mattress for $1500 tops - ideally closer to $1000-$1200 but would be willing to spend more for a great mattress.
I am predominantly a side sleeper. My last mattress was a Beautyrest Silver 900TS (Plush). I had it for three years and found it quite comfortable actually, but left it at an ex’s place
Sorry to hear you left the mattress you were comfortable on…! You may take some comfort in knowing that the 3 years you had it were likely the ‘best’ before it would likely begin prematurely breaking down…the problem with Beautyrest and other ‘major brands’ is that there is no transparency in the materials or construction. As a foam hybrid mattress, it’s almost impossible to assess the durability of such a mattress without knowing the density of the foams used. As you correctly determined, support is indeed very important; we suggest any foam in a potential mattress has no more than an inch or so of lower grade foams (for memory foam no lower than 4 lbs/cuft for normal range weights, and 5lbs/cuft for higher range weights) and if polyfoam is used, with at least 1.8 lbs/cuft density, just to ensure you have support. if this information is not available, this would personally be a major red flag on any mattress.
You can see the Mattress Specifications You Need To Know and compare them to the Mattress Durability Guidelines, to see how specific materials hold up over time.
I think I tend to like softer mattresses over especially firm ones, but because I’m a large man I think good support is important.
I’ve heard mixed things about any kind of pillowtop, so I’d prefer a mattress without that.
As you are looking for a ‘plusher’ comfort layer, it’s important to make sure it’s not too plush so that you ‘sink’ into the top layers and bottom out on the firmer layers below as this can also cause muscle and joint aches and pains and even alignment issues; and pillow tops also add a specific feel to a mattress whivch not everyone likes, so you are well off in avoiding those.
While @BillyIdol is not wrong that a latex or latex hybrid may be suitable for you, it’s always a good idea to try some different types and firmnesses of latex with in-person testing before making that decision, as latex has a very specific feel to it, and Talalay and Dunlop latex likewise have very specific ‘feels’ (Talalay is bouncier; the usual comparison is between angel food cake and pound cake). If you do like the feel, an all latex or latex hybrid could be a consideration. If possible, Taking a a day to try out different types of mattress locally and making a ‘short list’ of types/materials you like can help you to zero in on what you prefer.
Due to all the shakeups and issues in the business world over the last few years, we can no longer provide geographic listings for manufacturers and showrooms. This post from May 2021 on Los Angeles showrooms may be informative; also, several of the Trusted Members of the site, like Foam Sweet Foam and Biosleep Concept are located near L.A. in Riverside, and Flexus Comfort is in Covina, and there is also Mattress Makers located in San Diego as well. Also, most of the Trusted Members of the site do ship across the U.S.; these are all manufacturers and retailers with proven quality and transparency in construction and materials as well as much experience in assisting consumers in finding the ideal mattress for their sleep profile, and generous return and exchange policies. Hoping perhaps other forum members in the Los Angeles area can share their experience with other local mattress showrooms as well.
If you do have any questions on specific mattresses, and how they may suit your Stats (height, BMI, sleeping position(s) and any underlying health concerns) - (thanks for providing those!) - and your PPP (Posture and alignment, Pressure relief, and Personal preferences) feel free to post them here. Hoping you find your ideal sleep system in the near future!
~ Basilio