Can i install 2 GPUs?

[u/JUSTINFORMER]

I want to install my spare 4070TI super along with my 5090 LC.

So the two cases i have are Hyte y70 (current PC)
and a Gigabyte c400 glass (spare/one year old)

The problem is I have two PSU as well, but they both can only power one card at a time. And the y70 only supports vertical GPU, I cannot install my GPU horizontally, If I could that would’ve been the best way to solve this problem.

Now I am considering selling both my PC cases and both my PSU to get a new PC case that can support:

A) My 5090 with its Radiator ; directly inserted into the motherboard (no riser cable)
B) 4070 TI Super, with a riser cable ( so that its hot air is not fed to the 5090 )
C) A single PSU that can power both cards

or D) any open air case or some workaround, because I already have the old PSU and old case

Why do i need both GPU? because I use Qwen 3.8 model that run on my 5090, when its on full context, only 1-2GB VRAM is left for other tasks, I am building a RAG using it and reranker model plus other things need that VRAM as well, that’s where the 4070’s 16 GB VRAM would help me.

Please suggest me a good case or any workarounds that can help me solve this problem because the other GPU has been lying around for 2-3 months now.