I'd go for an ..80 card but I can't find any that fit in a mini-ITX case :(
24 is the lowest I would go. Buy a used 3090. Picked one up for $700 a few months back, but I think they were on the rise then.
The 3000 series can’t do FP8fast, but meh. It’s the OOM that’s tough, not the speed so much.
5070 Ti Super will also have 24GB.
Admittedly a little tempting to see how the 5070 Ti Super shakes out!
50xx series supports MXFP4 format, but I'm not sure about 3090.
I'd go for an ..80 card but I can't find any that fit in a mini-ITX case :(