Results: Battlefield 3
The $800 machine’s secret-weapon beta driver doesn't help it in Battlefield 3 (already a title pretty well-optimized for), though my $1,000 machine’s higher memory data rate does appear to help performance a bit.
The cheapest PC wasn’t even tested at 2560x1600, yet its tiny Radeon HD 7850 performs impressively at Ultra quality details and 1920x1080.