Re: Quadro vs. GeForce?
That 4000+ is going to bottleneck a GTX 260, definately a GTX 285. The Athlon x2s are quite old now really - like 3 generations old. Infact you may not see much increase from a 260 to a 285 because your cpu would be a bottleneck. I realise you probably dont have the cash to upgrade your CPU as well - so a new graphics card is the way to go, but getting a GTX285 is probably a waste as you may see the same performance on a lower card.
Do you do any rendering?