Compiler farm for gentoo

I want to set up a server farm for the purpose of compiling large software projects such as gentoo. I'd like some suggestions for the server hardware. Can anyone with experience in compiler farms chip in? For example, should I bother with SSDs or are they too costly to justify any benefit?

>>11
No, it does not. Donald Knuth wrote the entire TeX in a notepad. In a paper notepad, with a pen.