I would like some advice on what is the the very best hardware to get to build a super proxy server using RouterOS Beta.

I need advice on:

CPU
Memory
Hard Drive

thank you

Not sure about MT Proxy but if was squid

CPU not so important
As much memory you can fit (I have 4 gig in mine)
4 HDD's (not in raid array) 1 system & log, 3 others for cache.

above fo rme does over 500 users at about 50% cpu & 10% i/o wait