Which GPU is good in my scenario ?

Accelerated Computing CUDA CUDA Setup and Installation
#1

My application is memory bound, and involves lots of modular arithmetic, including inverse modulo operations.
Can I get some suggestions for choosing best Graphics card suiting my requirement ?

What all should I look for apart from memory bandwidth?

#2

The GPUs with the highest memory bandwidth are currently found in the Geforce 700 series, namely the GTX 780 Ti and the GTX Titan Black: http://en.wikipedia.org/wiki/GeForce_700_series