The 560 ti is a great graphics card , but its a great graphics card past its use by date since the next generation is here now . The Radeon 7850 is a better choice
If you crossfire two 7850's you only need a 650 watt psu
you are wasting money on RAM.
No game can use even 4 gig of RAM so you get no more Gaming performance by fitting more than that . Application performance can be better with 8 gig [ 2 x4 ] but more than that is definitely not needed
to much ram most i have seen used by bf3 (the heaviest game i have on ram )is 5-6 gb so 8 is heaps and personally i think the snipers look poxy the whole gun thing is gay just get ripjaws they are the same and same price! ati scales better than nvidia in dual cards but its personal preference i understand that aslong as it doesnt involve amd cpu's i have had sli and cfx and i prefer single card setups although 7 series raedon can full shut an unused card in cfx that sounds pretty cool (literally)