Dell have a sale at the moment. I wish I knew more about hardware!
For ut servers, look for the highest frequency/ipc cpus you can find, iirc it only runs on single core.
You could try locking each server to its own core or 2 cores, to avoid thread jumping by windows scheduler.
I dont think you even need more than 8 cores total for 4-5 servers.
Better disable turbo, look for the highest base frequency cpu.
Hyperthreading should be off, i think.
Use 32bit server only, 64bit has some issues i think.
Not sure if it runs best on 64bit or 32bit windows
You might need windows server 2003 maybe older for minimum issues.
Linux version has some tickrate issues, people used to avoid it.