Why bother with a 6870? The reference 7770 is nipping on its heels with current drivers and some of the highly factory overclocked 7770s can meet or beat the 6870 with ease while using less power and usually being cheaper too.
Aerocool is not recommended for PSUs.http://www.eggxpert.com/forums/thread/323050.aspx
Out of six tiers with lower numbers being the best, AeroCool is placed in the fourth tier. Are you sure that is the best quality model that you can get?
It's rated power delivery is high enough, but I'm not sure if it can meet its rated power delivery.