While Computational Science did address a highly upvoted question about which types of computation lend themselves to using GPU resources, I'm reluctant to push the boundary into specific hardware recommendations (and software to support it).
At least without further encouragement!
If not here, then there seem to be a few other sites with even a worse fit. Of course StackOverflow takes on a wide range of topics (often not without bitter objections), and there is the Software Recommendation site. I'll throw out Software Engineering as one I'm also familiar with, and add that it doesn't seem a good fit.
I have a fairly specific kind of application in mind, integer arithmetic of moderately large size (thousands of digits perhaps, not millions). I mention this because GPU integer operations are natively of fairly small size (think vectors of "single precision"), and library functions undertake a lot of mapping necessary to make those into support for extended precision integers.