Keep in mind that Milkyway is a "needs good DP Floating Point" project - those with the old Tahiti AMD cards (R9 280/280x and the HD varients) and to a lesser degree Hawaii (R9 290/290x/390/390x) will ROCK this project.
Ditto early Titan models.
Then there are the serious monsters, but I dunno if anyone rocks the high-end Firepro stuff....