You can use Smelter for GPU mining. I currently run my farm using smelter when mining quark based coins. Keep in mind though, the creator automatically gets a portion of the coins mined as a tax though.

As always, do your math, do it once, do it twice, shit do it 50 times before committing to mining to make sure your numbers are correct and you wont be in the ditch at the end of your mining session.