Rivatuner is fine. The g92 core should reliably oc to 750mhz, with some people going as far as 800mhz. Keep shader linked to core for best performance/stability. It's not heat bottlenecked, so aftermarket cooler won't help. As for ram, keep it near stock. Ocing ram does not produce significant performance improvement, unlike core/shaders, and the possible instability/corruption produced is not worth the trouble.