I would go with the G3258 because it will perform better than the A8 6600K in games and daily use. I believe the 6600K performs slightly better with multi-threaded applications (video/photo editing, and a couple games that utilize more than 2 threads), but most games don't use more than 2 threads anyway so the G3258 would be the best choice. It will also overclock worlds better than the 6600K.