All sounds like good hardware
I second the CHECK LINUX SUPPORT of the hardware. Things like on-board sound and ethernet contollers can also cause issues. http://www.linuxhardware.org/
is a good start, and just googleing the chipsets and motherboard models with the word linux added can help find forum posts.
If your UK based, then i could offer you pre-built systems, as my company is readying launching a range of pluto-powered solutions