New Machine (advice)

i'm looking at getting a 2nd computer this month for audio editing. (i've been looking at getting an iMac of some kind.)

my question is...
would there be any financial benefits to purchasing an older G4 or G5 and pumping up the RAM on that machine instead of buying a new iMac.

has anyone here sought out an older machine and had good results?

thoughts?

I posted a similar question just recently, I've only heard from one person but based on other research I think a lot of it will be down to what software you're planning on using. For example, if you were getting Logic Studio you'd probably be better off with the Intel iMac than a G5 but say you were going to go with Logic 7 or older then it might not make as much of a difference. This is mostly speculative on my part (being that I'm not yet a Mac owner), but I imagine newer software runs better on new machines/newer operating systems, non?

What is it you mean by audio editing? I think that may dictate certain requirements as much as the software you're planning on using...

i'll be running pro tools, and pro tools only.

LE or M-Powered I guess?

Part of what is governing my decision is how many simultaneous analog inputs I can have, and for that I'd be looking for a machine with FW800 and a fast hard drive so I can get a decent stereo image of a drum kit, for starters. But if you're only ever recording one or two simultaneous inputs or mostly doing MIDI sequencing then your prerequisites would be different right?