The following are the questions which come to mind for the hardware:
1. What kind of processing power do we need? Would a 2.0GHz PIV based
machine be OK?
If you don't intend to mix the tracks and apply heavy effects to them (compression, eq, etc etc..) 2.0Ghz
it's enough, actually I am able to record up to 6 tracks simoultaneously.
2. RAM is 512MB currently. Would it be enough?
It's enough but more would be better, and still it depends on how many tracks you are going to record and what you wanna do with it.
3. What kind of sound card would be a good choice? The ultimate
objective being to archive the audio as mp3/ogg.
No matter what your archive format will be, you will record in wave format.
4. Should the audio be captured from the mixer or from the amplifier?
Mixer, for sure. But if do not intend do keep each single track (each microphone) you record and you don't care of quality...
Software wise: which applications are there which can help in recording
the audio? For splitting/editing the audio I think Audacity is a good
candidate. Are there others of the same kind?
Ardour, a great and professional multitrack!! ...
Anything else we need to consider for the setup?
Simply a choice: record a single track using 4 sources (4 microphones) or record each micro into a track. To accomplish the first task you won't need nothing more than a standard audio card, for the second you need a multi input audio card
Thanks in advance to all,
/kS
regards
raffaele