BTW, reinforcements are here, 33 more 7950, I simply couldnt resist the price. Pictures to be soon. If I am correct, I will be at 80GHs now 
Gutsy move with asics around the corner. Right now you are looking at maybe $65/month gross assuming no change in diff. Expect that to be reduced to $20/month in about 1 month and less than $5/month after that. I'd be surprised if you see a payback period under a couple of years.