I'm currently mining with a couple R9 280X's and game on them also. I would go with a single MSI R9 290 GAMING http://www.amazon.com/gp/product/B00HPS4AFG for a couple reasons. 1. The R9 290 will be more power efficient while mining, 2. it has more VRAM and scrypt mining loves RAM, and 3. the R9...