pretty sure it's CUDA cores not CUBA cores
if you have lots of money, get 2 GTX 680's (somewhere over 1000 USD)
or wait for the 690 (expensive but worth it)
if you're on a budget, try a 560 Ti or a 550 (roughly 200-250 USD, 110-140 USD respectively)
make sure your power supply is sufficient depending on the card you buy. also ensure your CPU is powerful enough so that it doesn't bottlenck your cards.