New Graphic Card, whichh should I buy?

[radix]

ATi Radeon HD 5970 the most powerful card right now
but the problem is the card is not available to buy in market, u should try to buy used. and also u need cooling system if u have then ok, actually this card getting too much warm..

2x 6970s will out perform a single 5970 and are roughly the same price.

Because GPU's become finicky (IE: games will work fine, but GPGPU will fail) I would not suggest buying one second hand.