New bed or modifications for old one?

About 7 years ago I did a lot of research and ended up purchasing a queen 12" Bamboo Bliss (medium level 6) from Brooklyn Bedding. The bed was great for about 2-3 years for me. My wife still loves it and sleeps great in it. I started to have lower back issues and stopped sleeping in the bed. I actually started sleeping in a hammock, or on the couch in my basement and it completely removed the lower back pain I was having. I occasionally test out the bamboo bliss and without fail I wake up with lower back pain every time! Anyways, the downstairs hammock option has worked, but the wife and I are expecting out first child in October and I really want to be back upstairs so I have quicker access to assist with baby (She won’t let me put the hammock upstairs haha)

From my trial and error with other beds I believe I need a much firmer mattress (We were actually just on vacation last week and I was on a very firm coil mattress and I felt GREAT - the wife not so much). I prefer to sleep on my side. I can’t seem to find information on the bamboo bliss anymore. All I remember is that the topper is 3" of latex. I tried moving the bed to the floor, and its funny, both the wife and I felt it was SOFTER on the floor than on the bed frame. My question is would a firmer core/base help me out, or would a firmer topper? Also given that the wife likes the current feel/softnesss maybe I should look into some sort of split system? All the “guides” point to side sleepers needing more “cushioning” but that just doesn’t equate to my body

Edit: 5’9" and ~170lbs

I had a similar problem recently, lower back pain from sleeping on a too soft mattress, and really liking the feel of extra firm mattresses in a show room and at some hotels I stayed at. I was able to recreate that feel by adding a 3" firm dunlop latex topper to the cheap soft/medium spring core from an existing bed.

If your mattress has a zippered enclosure, you could open it up and see how easy it’d be to replace the comfort layer. Cutting an existing layer in half and replacing your side with something firmer would be a cost effective way to fix things if it works, but you’d also be throwing a few hundred dollars at fixing an older mattress, and the result might not be as nice as getting something new/designed to be a split comfort bed.

Thanks! I think I am going to try this. After further researching the bed we purchased the 3" latex topper is the part they change to adjust the firmness. Ours was 32ILD I believe. I think getting a 44ILD will do the trick. It is easily accessible.