I'm in the same boat mate, but instead of buying a rig, I invested it in to cexio, there's a lot of mixed feelings about them, but with 15GHs you'll mine around 0.03 a week at the moment, though that reduces on a daily basis so not too sure if that is the right move anymore. The good thing is, you can sell your initial purchase back, and the rate is quite low right now. If you decide to use cex.io, please use my referral link
https://cex.io/r/0/foysal/0/Or you might want to hold on to your cash and see if rigs reduce in price or do some day trading on bitstamp. That's one of my plans.
Where did you buy your equipment from and who are you mining with at the moment?
~Foyz