Hi ZT, happy to help.
1. I would like to go down the all-Bluetooth route, but I don't have the cash at the moment - I just use an Apple USB keyboard and MS mouse. But if that was what you wanted to do, then a basic setup would have only one wire coming from it, for the power. There is an external PSU, but it's fairly small, and actually looks quite nice. Network could be done wirelessly. If you were even slightly thinking about using Bluetooth and wireless networking, I would buy those ready installed in the computer, they're a bit of a hassle to fit later.
2. I would love a Mac screen! But I use a Philips 17" widescreen LCD via DVI - this screen has two inputs, so I run a TV tuner into the second port. Refer to the Apple Discussion forum, as there's a fairly large list of screens which are known to work; some LCDs can have problems with the mini.
3. The networking is really straightforward - it's basically plug and play. I've used it on a network with PCs and another Mac, and it really is easy to use. At the moment I have an old iMac with a 120Gb hard drive in another room, and both machines are joined to a network router, which also shares my internet connection. iTunes is set up to use the 120Gb as its storage directory, and it works pretty flawlessly. You can get network attached storage drives - basically a netorkable external hard drive - but I haven't seen any that work perfectly with a Mac, and for the price you pay, you could buy a cheap old computer to do the same job.
4. Have a look in the Computer Audio forum for the M-audio Firewire, there's a lot of info there. Basically, it acts as the soundcard, completely bypassing the mini's (not fantastic) sound output. You can then join the M-audio to your amplifier using normal audio outputs, or use its digital out to join it to a separate DAC, and then to your amplifier (which is what I do), or run your headphones straight from it. It also has a couple of audio input channels for recording (haven't tried these yet). They're available for around $150, and definitely worth the money! As for connecting to a powered sub, that really depends on the sub itself. If it's one which comes with its own satellite speakers, it'll be a matter of hooking it straight up to the audio outputs of the Firewire card; if it's a proper hifi sub, there is a second pair of audio outputs. I've just remembered that you can download the manual for the M-audio Firewire from their
website .
Hope this helps, any more questions, please feel free to ask!
Andrew