Computer Do Over

I have been partial to Macs for years although I run PC for CNC/CAM. Seeing as you already have a monitor and keyboard/mouse, I'd get the mini and load it full of RAM. I run my mini "headless" on an AV system, connecting it to the monitor when needed (rarely). Otherwise I control it either through and iPod touch or via screen sharing (built in) with the iMac I am on now. It is easy and seamless. FWIW, just yesterday a luddite friend of my mine (whom happens to be a respected vacuum tube dealer) commented to me about how much he liked the iMac I talked him into over a PC, and that it had never frozen or crashed in over a year!
Snow Leopard is the current operating system (10.6) that will come with most all new macs being sold. My girlfriend bought a refurbed one, and it has been fine for the 10 mths she has had it.

is there any other choice? mac all the way. for a server, get a mac mini. once you have the system up and running, you don't need a keyboard or monitor. you can use another mac to control the mini. plus, if you have a iphone/ipod touch/or will be getting the ipad, you can control the mini thru the remote app to play itunes (i use my iphone all over the house). plus, you can use the vpn app on the iphone to actually control the mini. it allows you to have the mac screen to start any app or to control the mac to reboot if needed.

get a mini for your server, imac for you desktop.

Please consider the Dell Zino (Insprion 400), it is a better value then the mac mini. I recently got a scratch and dent one for $220 (windows 7, wireless card) and it works great. If you want to go Mac, I second the idea of others that the iMac is the way to go, thinking refurb to get the price down. I am amazed what the little zino can do. Since you have an external hard drive with all your music, you would be set to go.

there are a couple of things you need to think about if you are going to use this in your audio listening room (which i wouldn't do btw). dells, laptops, towers, etc... most of them have fans that can get noisy. the mac mini is quiet. how about form factor? is the dell or any other pc the size of the mini? not even close.

if you want to save $$$$, go to craigslist and search for a used mac mini. you don't need an intel mac mini. as a server, you can run leopard or tiger even on a 1.42ghz mini with no problem. i have seen these for $200.

if you want to upgrade your mac to use amarra, then you might want to buy a intel processor based mini.
i would then buy an ipod touch/iphone/ipad to control the mini for your audio/video needs. i have used a touch and currently use an iphone, but in a couple of weeks, i'll be using the ipad to vpn or remote control the server.

for a few more $$$$, then get another mac mini or an imac for a personal desktop machine.

i would not use and i don't use a computer in my audio room for a lot of reasons: can be noisy, will have multiple drives or a nas setup, might need a keyboard/mouse/screen, etc...

if you put this server in a den or even in a utility room, you won't care if there is noise or not. as long as you can get to the machine from your iphone/touch/ipad, and you route the signal over a wired connection or wireless, the data will be transferred without any degradation from these locations.

Actually there are quite a few PCs that are as small or smaller than a Mac Mini. All of them are cheaper as well.
This one of them Acer Aspire.

Here's another called the Fit PC

Since you're using a wireless head unit, I'm not sure there will be a real difference in using any of them. I suspect not.
There's quite a few others out there as well. You could go with a full tower and just store it away using it as a server. Noise wouldn't be a factor in that setup. That takes the equation out of it having a fan or not.

For a server, I would opt for a more powerful full tower machine. And yes they can be whisper quiet as well if need be. Reason being you may in the future find more uses for it, other than just a music server.

I know many here are hell bent on a Mac, but there's always more than one way to skin a cat.