well, I used to have a HD 4850 and later HD 7950 and currently using GTX 780 in my winXP/win7 dualboot PC (also using auzentech x-fi hometheater hd, my favorite x-fi sound card, it has ca20k2 chip btw) and after switching from 4850 to 7950, I noticed some old games stopped working correctly, most notably Serious Sam (broken graphics in OpenGL mode, stutter in Direct3D mode) and NFS Hot Pursuit 2 (broken graphics). Sold the 7950 to cryptominers at a profit and bought the GTX 780 and havent had any issues since. But Im starting to regret selling it, wish I still had it to test more games and find out all that are broken and document them, as mentioning just 2 doesnt sound so convincing 😀 (p.s. just remembered, Far Cry had corrputed distant textures when you zoom in with binoculars or sniper on 7950 too, that makes 3 games that I know of, and who knows how many that I havent tried)
At any rate Im fairly sure R9 280X works with the 14.4 catalyst for XP32, tho, you can always get a 7970 too, not like theres much of a difference. But I think a GTX 980Ti is probably the best card for a winXP/win7 dualboot, Im thinking of upgrading my GTX 780 to that once I find one on the cheap 😀 And I don't like using multi-gpu cards and SLI/Crossfire setups, very few games support that and even those that do may display microstutter issues and low min fps, its best to just get one fast card imo. 3dfx is the exclusion since they don't use AFR