What kind of a bennifits do you get if you go the x16 path?
also, what exactly is the difference (pros/cons) in going w/ SLi over Crossfire?
Not exactly sure on this one. It all depends on the total bandwidth of the card. It was my understanding that an 8x vs 16x isnt a different on today's cards.
I run a crossfire rig with 1900's, my motherboard only supports 8x - 8x mode. Newer ones support 16x - 16x.
I get fairly good performance. I would suggest trying 1 card first to see if this suits you. I game at 1600x1200 and like my AA and AF, so crossfire is good for me. If you are not a high res gamer and game at 1280 or 1024, I would suggest trying one out before buying a second.