steveagain :
JackNaylorPE :
You really don't have a choice..... the you have the 7870 and that being an AMD card is capable of CF but not SLI as thatz nVidia's shindig.
You'd have to dump the 7870 and buy 2 new nVidia cards to SLI.
Ok I dont have to much of a problem with that as cards like the raedon hd6950 2gb ddr5 are on sale right now at $190
Neither if your buying a new card always buy the best card you can Xfire and SLI bring alot of problems eg stuttering, heat issues. wasted resources that a single card wouldnt experience. If you Have to use one use SLI as it is more refined but when ever you dont wont to buy the same card try and get a more powerful single card rather than two weaker ones.
The Doctor