Which would be best, visionTEK radeon hd6970, 2 pny gtx 460's overclocked in sli, or pny gtx 570?

ok, so one of my family members has opted to allow me to buy a graphics card off of their dell prefered account, so my usual trips to newegg.com are not available. On dell's website they have a 6970 for 399, a gtx 460 at 180, and gtx 570 for 369. Right now my setup is as follows.



asus p5n-d motherboard

intel core2duo e8400

6 gigs ddr2 ram

i currently own a gtx260 and 8800gt graphic cards

and a 600w power supply

running win7 x64



The games i mostly play are

Starcraft

Warcraft

Portal 1+2

CoD 4 through black ops

Halo 1+2

L4D

Fallout 3 and new vegas

Dead Space 1+2

The force unleashed

Bioshock 1+2

Mass Effect

Metro 2033

Half Life 2

Alien vs Predator





I also have a triple monitor display right now, but that can be knocked down to 2 displays.



Now the reason i cant make this decision alone, is because the ati graphics card, i havent used anything ati in a LONG time, and im not to certain if i want to use ati cause my motherboard supports SLI. I also know that the 460's are cheap and didnt know if they would be good for sli config to match or beat the 570, the room between my graphics cards is limited. These games i would like to play on the highest possible settings on high resolution, my gaming monitor supports 1080p. Any input would be GREATLY appreciated and welcomed. The only problem is they have to be ordered off of dell's website, the link to the graphics cards is



http://accessories.us.dell.com/sna/category.aspx?c=us&l=en&s=dhs&cs=19&category_id=5406&sort=-price



If you find anything else that would be great, id love the suggestions. My spending limit is total of 449. Thanks for the help!!!|||ur gonna save some money get 1 gtx 460 or 560 ti so it wont bottleneck ur dual core processor too much and u still can play those games maxed out with 1 of those gtx 460 or 560