a server to host games/ files? nothing much , any old pc with 256 RAM , 1ghz CPU a network port and 80GB or more HD space and of course a low ping DSL connection for games ,or T1 for files , about 2500 tt , don't need a monitor self if you have other machines around , though if your talking about RAID storage and PATA/ SATA you want more cpu power , and a 2.4ghz + 512mb RAM game server could host multiple games at once , thats around 3500-4000 tt .
A server machine to do serious work like render 3D , CAD or photoshop , you want a server chassis , a dual opteron/Xeon mobo , 2 opterons/xeons , 600 watt or so power supply , 2 gigs of RAM , 2 or more SATA hard drives in RAID 0 etc , it would all come up to close to 10 000 tt
though i'm no guru , don't take me too seriously :p