Please remember that any mention of competitors, hinting at competitors or offering to provide details of competitors will result in an account suspension. The full rules can be found under the 'Terms and Rules' link in the bottom right corner of your screen. Just don't mention competitors in any way, shape or form and you'll be OK.
5870 and £130 worth of beer for the weekend? http://www.overclockers.co.uk/showproduct.php?prodid=GX-136-OK&groupid=701&catid=56&subcat=1502
Other than that, I'd agree on 6970 or 570 depending on whether you're ever likely to go Eyefinity or 3D respectively. If neither appeals, do a search to see if you can find a benchmark of your favourite game and these cards to see if one performs better in that game.
Which out of 69xx and 570 is quieter and cooler running?
Edit: Also how would a pair of 460 1GB or 6850's compare?