[svennek]

In short... Proliant Micro Servers (the black "g7" not the silvery g8's)...

Cheap, 4 bays, ECC mem and an (optional) mangement card... but I don't know if it is fast enough for you (probably not....)

[IbJacked]

Thanks! I've seen a few comments that also mention the Proliants, people seem pretty satisfied with them. And it might not be too slow, my current Plex server is my 2010 MacBook Pro.