I've started with a basic MCPC which is based on a Dell Power Edge Server (purchased for only US$350!) with a:
1) Motherboard / Case: mBTX Motherboards are the newest format and are very quite thanks to a massive CPU Heatsink and slow fan. I'd suggest the Intel D945GBO as a great value alternative as for US$150 it also has Raid 5 and S/PDIF. The case is a black mini tower format that is very quite and hids nicely behind my black EP500 / MT60.
2) Processor: Intel PentiumD280 Dual Core grunt came with the box!
3) Memory: 256MB Mem came with the box, have ordered 1Gb for $100 (expensive as the Dell server uses ECC memory). though I've had no probs playing everything with the std 256!
4) HDD: Got the 250GB SATAII drive and can add at least 3 more for around $100ea but would like HW RAID 5 (note: may use the following XP Hack for SW RAID 5 (http://www.tomshardware.com/2004/11/19/using_windowsxp_to_make_raid_5_happen/)
5) Control: I've spent another $20 for USB keyboard/mouse (and 5mtr cable) but am on the lookout for the Microsoft Infrared keyboard & receiver
6) Sound / Video: Spent $15 for secondhand S/PDIF soundcard (all the decoding is done by the Yami V2600) and $50 for a fanless Video card that supports S-Video/Component to connect to the Yami V2600 as I wait for the first of the new HDMI based cards to arrive!
7) Software: I just use XP as the OS and find I have been using both Media Player (mainly to Rip CD's) and Nero Home as the GUI (come bundled with Nero so for me the costs = $0). Also tried Media Portal and even considered using just Media Player (but would need to buy the DVD Decoder).
8) File Formats: I'm ripping all my CD's as "Lossless WMA". Yes they take 35MB not 5MB per song, but disk is cheap and to me the difference is very noticable on the Yami/Axiom setup. No point in have good equipment if you feed it crap. With the right S'W running in the background you can also just copy the DVD's across to the the HDD then rename the VIDEO_TS folder as the DVD Name - simple, easy and perfect quality.

It has all taken a bit of fiddling around and is not the most stable so I will reinstall the system once I've got it going how I like it.

Nathan

HT:M80,VP150,QS8,EP500 Outside:4xM3 Office:AudioBytes, Rumpus: M60,VP150,M22 Portable:2 x Airs