Currently the Megahalems cooler is not accompanied by a directly attached fan; still waiting on those from Tigerdirect.
Ok so the question is what type of CPU temps should I be expecting? . I ran Prime95 for 15 mins before I stopped, deciding that my temps were, in the eyes of a first time builder with no OC/stress testing experience, abnormally high. 15 minutes of prime95 brought my cpu temps up to about 85C. Idle temps are 30-35C
Would a single direct fan on the heatsink make that big of a difference or is it likely that I screwed up with installing the heatsink? The only fans inside at the moment are the original case fan and I guess the PSU fan
You need a fan with that type of cooler, amigo. Why else would they design it to accommodate 2 fans? One is a minimum, 2 is always preferred. It's basically the same idea with all heat-pipe/direct contact coolers. Even my little CoolerMaster Hyper 212+ needs a fan, and this design isn't too far from what you are using.
Also good TIM. 85 seems really high, but throw some fans on the Hegahalems and see what happens. I always say, do your research. For this application you are going to want great static pressure. CFM's don't matter too much, but the amount of pressure matters more in this situation.
I've heard the coolermaster R4's are good, so are the scythe slipstreams. Hopefully those will be some good starting points for you.