you'd need a bloody powerful computer to run 10 servers at once.
I'd suggest a couple of Opteron 8** series processors, maybe 846 or 848. the most powerful are the 852's which are really expensive. the 8** series Opterons are 8-way (each CPU emulates 8 CPU's, to get 8 instructions processed at once)
and a dual socket 940 motherboard, like from Tyan
with about 2 x 2GB sticks of RAM each CPU (must be ECC for socket 940) - 10 CS:S servers would take up a crapload of RAM
there is even a quad socket 940 board from Tyan, but it's expensive, and should only be used for dedicated servers (which I'm assuming you're doing)
all in all, I'd say, unless you've really got money to burn, it's not really worth it.