the APU performance is tied directly to the speed of your ram. Meaning, you need to get a minimum 2133 or 2400 DDR3 to get any decent gaming performance out of it...it is not just the amount of ram, but the speed of the ram that really matters.
I have the same setup using ddr3 2400 memory, and my 3dmark scores are pretty impressive. Perfect for casual gaming.
Processor: AMD a7860K (stock 3.6ghz) running at 4.4ghz using stock cooler
Motherboard: ASRock A88M-G/3.1 FM2+
Graphic Card: Built into the processor. The AMD R7 APU. (Stock 750mhz) running at 900mhz.
Memory: Kingston Hyper X Predator: 16GB DDR3 running at 2400Mhz at CL11 speeds.
RamDrive: 4GB (100x faster than SSD). Used for Windows temp files, browser temp/cache files, and Photoshop Cache.
Thermal Compound: Arctic Silver Ceramique 2
Case Fans: 3 (120mm) high performance fans from Enermax
Passed all stress testing:
Prime95: For over 3 hrs
FurMark: Burn-in/GPU stress test for over 10 minutes
AMD Overdrive Stability Test: For over 2 hours
Memtest86: For nearly 9 hrs
3DMark Benchmark Scores:
Sky Diver: 6763
Cloud Gate: 8054
Fire Strike: 1740
Time Spy: 730