Hmm... If you're planning on having it as a dedicated system, you could either go with a Mac Mini ($600) or an iMac (which I feel is the best bang-for-the-buck in the Mac lineup, and extremely versatile), or you could get a relatively low-powered PC. Either way, I recommend two external hard drives of at least 1TB: One for music file storage, the other to serve as a backup. Depending on how much music you have, you may need two external RAID boxes for ganging multiple drives together; you can choose RAID level 0 or 5 depending on whether or not you want redundancy. None of the Mac's currently have eSATA interfaces, which would theoretically yield a higher data transfer rate to the drives, but Firewire 800 or USB 2.0 should be more than sufficient for most uses.
Music servers don't generally require a lot of CPU power, so you can get a relatively inexpensive computer from a CPU, RAM, and graphics standpoint and put the money in your drives and backup system. The other way of looking at this is that you don't have to dedicate an entire machine to this purpose, and can use it as a general-purpose computer with the music server function in the background. Whichever system you go (Mac or PC), it will likely work just fine for you.
Michael
Music servers don't generally require a lot of CPU power, so you can get a relatively inexpensive computer from a CPU, RAM, and graphics standpoint and put the money in your drives and backup system. The other way of looking at this is that you don't have to dedicate an entire machine to this purpose, and can use it as a general-purpose computer with the music server function in the background. Whichever system you go (Mac or PC), it will likely work just fine for you.
Michael