Im using an HP DL320 4th gen and it makes an ok for a small server
Pentium D 2.8Ghz
8gb DDR2
1x 80gb for OS/ISO
1x 500gb for vm's
No backups or anything, gigabit d-link switch for backbone. Works well, pretty quiet. but it gets warm.
I have this server,
http://www.newegg.ca/Product/Product.aspx?Item=N82E16816110047
and its DEAD quiet, fans set to quiet managed mode.
Installed is a quad core xeon and 16gigs ddr3 ram and 2 x 500 gig drives in raid 0. ITS FAST and quiet.
Dash