You can run with even just one stick, but why bother?
Also, the role of stress testing is not understood by the tester. You stress test to check for stability, not speed.
Using SSD for scratch isn't necessarily going to speed things up either as the write speed of most currently on the market cannot do any better than an HD running at 7200 RPM. I tested exactly that setup (well, I ran an i7 920 2.67GHz, overclocked close to the XE he used)and found the SSD about 0.2 sec slower in a filter that took 14 sec on that system.
Now, off to work.....