I've had (mostly lower) back problems for the last 20 years or so. My old desk chair was great, but it eventually fell apart. I now have an Amazon chair that needs a new home in the nearest dumpster. I'm considering a Secretlab Titan Evo, but I'd like some input before I make that investment.
So, what are you sitting on, and what do you think of it?
A layer of square gel, a small thin square pillow and then an orthopedic u-cutout gel cushion on top of that that takes the pressure off the spine area. It makes it tolerable for reasonable lengths of time. I can put this setup on any chair that has a relatively flat area and it works great. I think the most important thing other than what's under you is the ability for the chair to maintain a straight position to fortify proper posture.
I bought the fantasy lab big and tall because it has a giant seat area I can fit my layered cushioned creation into and it accommodates a lumbar vertical support cushion as well and is still roomy. The actual bottom of the chair is very hard and super uncomfortable if you aren't using some kind of additional cushion. As a stand alone chair I would rate it very uncomfortable but if you need the space to layer on your own stuff its a perfect host. It is solid and adjusts decently.
As an edit I will add that you should experiment with bottom cushions, regardless of how good something feels at first with sitting for extended sessions after about an hour even the nicest gel slabs and comfort cushions compress and everything feels hard. I played with many different variations until I settled on the gel bottom layer, the typical cotton seat cushion in the middle and the orthopedic memory foam / gel comfort layer bottomed u seat on the top. I was using memory foam pillows and all kinds of in-betweens. If you cannot find a comfortable lumbar support that works for you (There's decent orderable ones to put behind you, and they are fairly cheap) get the thinnest memory foam pillow you can find and wrap it around your lower back, it got me through for a long time till I found an ad-able lumbar support that worked. This is what inspired me to find a giant chair, more of like a commanders bridge chair than a small gaming chair. Even with all this though I cant really deal with it after about two hours so I definitely game less these days.
Bulging L4-L5 left side dominant into severe sciatica.