I too recommend the Linkstation.
I use an LS2 MIPS running Twonky & firefly, using Openlink.
Currently building up an LS Pro as a replacement. Using a modded version of the buffalo software, with buildtools, Twonky, firefly all on the box. Firefly was easy to install from source, it has a Gigabit port, is silent, and is much faster than the LS2.
Just wish I could afford a Terastation Pro…
see http://www.linkstationwiki.net & forum.linkstationwiki.net for all the info.
Cheers,
Alistair