Same thing happened to me with Nanopool, except I didn't put up with their low payouts for an entire month...
I don't mine Ethereum, but I have mined two other Ethash coins - MUSIC and UBQ - and I really like Pool.Sexy for both.
Oh, and you are missing out on at least 5 MH/s per 570 by not doing the BIOS mod.
If you do the calculations (unless I am doing it wrong) MUSIC and UBQ are currently still not as profitable as eth. Are you seeing something differently?