prime95 is a good stress tester, along with superpi. what you'd want to to increase your ram is go into the Frequency/Voltage Control Menu in your bios, then go to the memory settings, then from there you can increase the frequency which is just like increasing the clock speed of your cpu. Increase it bit by bit and if it doesn't boot increase the voltage, same would apply if you want to lower the timings (which would increase responsiveness).
As a side note, you probably won't see too much increase in performance as it will be minimal, and the amount of ram matters in most tasks more than the speed of your ram.