Help for a newb

[EaTCarbS]

Two i7 rigs with at least 12g ram each should run 20 clients without much problems. I wouldn't do more than 10 on one machine.

[Bollwerk]

The post you linked is for a 10-box test.
The more clients you're running, the more benefit you'll get from hyperthreading.

True, but since each WoW client can use at least 2 threads/cores, it seemed logical that similar results would hold for 5 boxing, as with 10 boxing. As I mentioned, it made a significant difference for me to go from a 2500k to a 2600k and I only 5-box.

[Ualaa]

When you're talking the cost of a CPU, Motherboard, Ram, Video Card, SSD, etc...
An extra $100 bucks or so... that's not really a lot of money comparatively.

If you have it to spare, the i7 2600K is probably the way to go.
If you're on a tighter budget, the i5 2500K is still a really nice processor.