Xeon 5520 (Nehalem) vs. Harpertown

I am ordering parts to build a dual quad system to run game servers on, and the more I can run from this box the better. Obviously the Nehalems are going to be better as they are a newer architecture, but how much of an increase in performance am I going to get comparing it to say a Harpertown or something similar of the same speed?

Considering game servers are assigned to various cores, and generally do tend to use a lot of the processor, im just wondering how much better these nehalem's are, and if its worth the extra money for them. I dont really get hyperthreading, and im not even sure if it will help much (if at all) with game servers, and have even heard from someone that it could possibly hurt the performance.

Anyways, hoping you guys can help!

Also, just a random question to throw in here. Can you run a dual quad setup in a 1U server, or am I probably going to be looking at a 2U?

did you get any answer?