The 512MB for the GPU will change when you increase the amount of RAM from 8 to 16 GB. The max you get is about 3.9 GB for the GPU.
You can tweak performance in terms of overdrive but that is about all I will say on that subject.
You can force somethings by changing your power options from Balanced to Performance but heat is not your friend.
Once you have done anything to boost performance check the temps with either Core Temp or HWMonitor to ensure proper operating temp is maintained.
AMD A10-5800K, XFX 7850 Ultra OC Edition 975MHz, 16GB RAM, Win 8.1 Pro 64 bit, MSI 7778 motherboard, 500W PSU, HP P7-1235, CCC 13.12 WHQL