I have been asked this a few times and till now I have been shying from posting this, but here it is now, the details of the MCE I build a few months ago (in Feb. 2005).
Motherboard: I got a 939 pin MSI K8N Neo4 Platinum
Processor: AMD Athlon 64 3500+
RAM: 1 GB, DDR PC3200 (Ballistix)
OS - Maxtor 80 GB
Data - Two 200 GB (each) in RAID 1
Graphics Card: nVidia G-Force 6600 (PCI Express) with 256 mb RAM
Case: Silverstone LC10M , Silver Colour
Power Supply: Fanless Power Supply - ST30NF
Sound Card: Creative Audigy 2 ZS TV
Tuner Card: Hauppauge WinTV-PVR-500 (Dual Tuner Card)
There you have it. I had done loads of research and found for my budget this was perfect. The idea being in a couple of years this box can move into the study and be a powerful desktop/server then.