Ah, through gift certs. When you say GC I read game credit, not gift certificate. Either way, you are still with a carryover that you can only top off with a NC run. A gift certificate is 3000 for $20, so unless you have RP in multiples of 3000, you are going to have a carryover that is useless until your next NC run.
For the record, and I know I'll be cruicified by some, I still don't think D3 or D2 rewards should be the equal of D1. It's just tougher to keep succeeding in D1. Better rewards, yes; equal, no.