I find it hard to recommend AMD for anything much. Even if an AMD chip is overclocked to compensate, the power consumption gets a bit crazy. Intel I3/I5 spanks them so hard and generally uses less power while doing it Something like an I5 2400 and a simple P67 or Z77 mobo would be great. Yes, it costs more, no it can't really be overclocked, but it will run cool and not use much power...and it will perform really well I think I would pick the 560. It performs better than the 6870, by (generally) a bigger % than the % extra power it uses.
PSU.... I wouldn't buy anything less than 80Plus Silver a good quality 500W unit should be fine.
It's hard to buy a bad mobo these days... most are good