OMG, with your 10 CPUs it's even gonna be a while before you get these 5 BTC back.
CPU mining is just that, plain stupid.
of course i only had a quick glance and assumed if the best can achieve 45$ after a while i can get 450 $
but I did not look at the timeframe yet..this isn`t monthly right ?
You are making about 0.20 BTC a day with each of your 5870s. On average, you are paying 0.10 BTC per day for electricity per card (no flat).
Mining on a powerful CPU doesn't even give you 1/100 of the hashing power, while consuming roughly the same energy. So in one day, you will make 0.002 BTC per CPU while paying 0.10 BTC for electricity.
These numbers are based on measurments and calculations I did myself.