How does the Core 2 Quad do with 5 clients?

[merujo]

I had a q6600 that i used to run my 4 slaves, and i had my main on my C2D. On TBC it was flawless, and even when WotLK came out i played without problems till i met Dalaran and Wintergrasp. It's impossible.
Having only 4GB doesn't help, but i think one of the major factors is also the HDD. Upgraded recently to Win7 and came to the conclusion the HDD i run my copies from is kinda slow, even being a SATA drive with 7.500rpm.
I just couldn't continue like that, so i grabbed an extra LCD, put it on my main pc and run 2 clients, my quad now handles just 2 clients and my MacBook Pro handles the 5th client.
It could be all sorted with 8GB on the quad? Probably. But the HDD takes a major roll as well, perhaps a WD Raptor may also help a bit or a SSD.