a nicely configured dell poweredge t610 with xeon e5520 quad core, 6gb ram, mirrored 500gb hard drives, should be about $1800.
if you want to build a PC for this, i suggest
cpu: core i7-860, $280
motherboard: msi h57m, $160
ram: gskill 2x4gb ddr3-1333, $360
drives: wd re3 750gb, $400 (for 3)
once you add a case, 500w ps, etc. you should be around $1500. use intel matrix raid to mirror the first 50gb or so of 2 drives and use that as your boot device. then mirror the remaining space of those 2 drive and use it for common storage. use the 3rd drive as a warm spare or for stuff that's not mission-critical.
core i7 and xeon e5540 are both based on the same CPU family (nehelam) and both are quad cores with hyperthreading. core i7-800 series is a newer revision designed for the mainstream consumer market. the i7-860 will give you performance better than a xeon e5540 but you won't have the option to add another CPU (only xeon's support multi-sockets).
xeon e5540 specs
core i7-860 specs
I work at a small office (20 people) and we use a desktop PC (with good configuration) as a server. It has Windows 2003 Server and VMWare installed (just this). There are several virtual machines (Win2003) for firewall, e-mail, DC, Webserver on it. However it is old and we are thinking about getting a new desktop PC for a server. It is going to do the same work. As far as I know Intel Xeon Processors are good for server machines, but there are a lot of factors that should be considered and I don't know anything about. Like HyperThread. Do I need it? And which processor with what compatible MotherBoard should I get? 2x4GB ram or 4x2GB? I can easily build a PC, but I don't know much about the detailed specifications so any suggestions would be nice. I think the PC should be up to 3000$.
. Thanks again 
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