I picked up a 4090 a few months ago specifically for stable diffusion. The generation times are insane. To compare I used a 3060 mobile and a 7900xt.

AMD compatibility is very bad right now with ai. Progress is being made but it's slow. If you're checking back in a year or so, and it's been fixed, I would honestly pick up a second hand 7900xtx and it would blow your 970 out of the water at a much better price point than my 4090.