For kicks I threw together the parts to make a amd apu gaming system. Thanks to my need to buy Windows for the build the cost was fairly high, but I would get console crushing power in a htpc size case. (all I did was put it together in my Amazon cart, I didn't actually build it.)
Here was the parts list I came up with (I splurged on some stuff)
AMD APU 3870k $119
Asrock Socket FM1 $90
Corsair Vengance 8gb $47
Seagate 2tb 3.5" $100
Black Micro ATX case w/220w psu $49
and here are the extras.
AMD 6670 $70
(for crossfire, should give a sizable fps boost to games)
Corsair 430wt PSU $40
(if the included psu isn't enough, the apu only draws 100wt)
Windows 7 64bit $100
(I don't have any specials to get it cheaper)
Grand total is under $650 and isn't too shabby considering what it is.
I don't plan on buying it, but considering the base setup is only $410 and can run Battlefield 3 on low at 720p 30fps is pretty impressive.