I would recomend staying away from 1866 ram unless you're only going to get two sticks. I've been trying to get my 4x4gb 1866 gskills running for a month now to no avail. Try 1600mhz with the smallest timings you can find for a good price. There's not too much to buying ram. Just remember that the ram will be quicker if the timings are lower. For example mine are rated at 9-10-9-28. You could probably find some as low as 7s but you'll want to balance it with price.