I once had an NV FX5500 that refused to work properly on one motherboard I owned (a PC Chips with SIS chipset!), but was fine in every other mobo I tried it on.
My trip-up question was the 3 current games one - I most play legacy stuff
As to how I'd spend £500 - well, I'd probably drop £350 on a mate for their Christmas present, and then treat myself to a new graphics card with the rest. Maybe a low profile 7750 so I could swap my gaming rig to a low profile matx box - that'd be pretty sweet