Thanks for considering DLX. Based on the information so far, your height, weight, and sleep position and the fact that you found the Beautyrest comfortable until it started sagging, there is a high likelihood that you’ll find our mattress comfortable.
Both the Classic - Two Sided Mattress and the Premier - Hybrid Mattress are great mattresses. For a Queen, it is well below your $2,000 budget. We generally lean toward the Premier because of the ability to adjust the comfort, but many people also love the Classic and customize it by adding a topper. The DLX Classic has a more old-school, coil-forward feel and is a bit bouncier than most one-sided mattresses. Based on what you’ve shared, the Firm sounds like the right direction for you. Many people add a third-party topper if they need a little more cushion. The old adage applies here that it’s easier to make a mattress softer than it is to make it firmer and more supportive.
The Premier is also a great option, as it allows us to adjust the comfort on one side by splitting the 3" comfort layer. You can also purchase replacement layers down the road to refresh the mattress. As side sleepers, we’d recommend the Premier 14", as it still provides good support as long as the support between the mattress and the floor is adequate and the taller mattress offers a bit more cushioning for side sleepers.
The difference between the 12" and 14" models is the coil height. The 14" uses an 8" coil, while the 12" uses a 6" coil. The shorter coil gives the mattress a firmer, more supportive feel, while the taller coil provides a bit more cushioning while still offering good support. We typically don’t recommend the 12" for side sleepers unless there’s a strong preference for a firmer feel.
We’d probably recommend starting with split firmness with half Medium and half Firm. Keep in mind that if you need extra firmness, you can upgrade one side to latex. Latex is known to be buoyant and resilient, meaning you sleep more on it than in it. This upgrade can be done within the first 120 days for the cost difference between the Premier and the LatexLux, as the mattresses are identical beyond the 3" comfort layer.
If you’ve had issues in the past with mattresses sagging, regardless of which mattress you choose, we strongly recommend making sure everything between the mattress and the floor is providing proper support. This has a major impact on performance and durability. If you don’t mind sharing what you’ll be using such as a platform bed, adjustable base, box spring, frame, etc, we’re happy to take a look. Unfortunately, a lot of products on the market don’t provide adequate support. That doesn’t necessarily mean you need to replace your entire setup, but you may need to make a few adjustments or replace one component. We’re primarily concerned with the support directly beneath the mattress and how that support transfers to the floor. Most of the time, the exterior bed frame itself is not the issue.