If you edit audio, a G4 with Peak is the best 2-channel hard disk recorder out there. I keep my G4 around for audio work, using ancient 5V PCI IO cards that won't work in any modern Mac or PC. MAudio Delta line is the best audio IO HW you can buy, and they work on any x86 or PowerPC box.
A G3 with 128M makes a decent DVD player; my kids each have a G3 laptop for that purpose. However you really need a G4 to surf today's web: watching Youtube or playing Flash games. The G4 has marginally faster performance on MacOS 9 but the functionality of OS X far outweighs the speed hit.
Something to consider, that G4 is going to use a fair bit of power. Around here 1W of constant power usage costs about a buck a year. At 200W for a typical tower, it's going to set you back a bit to keep it running.I have two computers which are 400W each....
If the G4 has an ATI graphics card, you could try MorphOS (http://www.morphos-team.net/). (and dual boot with OSX)
Okay you have me interested in regards to the audio editing on the G4. I do have an audiophile 2496 in an intellistation (as discussed a long time ago)... but if what you're describing is better, I'll gladly take the plunge.
I'm not sure which delta card you're referring to, the latest one I believe is the delta 44 (http://www.m-audio.com/products/en_au/Delta44.html).
How much RAM is in the G4? You'd want at least 256MB, more like 512MB to run OS X decently.It has 1 GB of RAM (I guess writing "a gig" is a little bit too colloquial). Nothing too shabby. It's a decent computer, actually. It was the first time I saw PCI-X, so that was a good quick learning experience (can't believe I never saw it before!). It also has a crystal audio chip... that took me by surprise.
Thanks to this thread I set up my G4 tower as a Youtube/IMDB/PBSkids machine for my kids. Motivational.
Just remember that hardly no updated apps are written for the PowerPC processors any more, so you will have to go with old versions for most. I am still running a g4 mac mini as a web server but neither apache or mysql is updated for ppc any more. But if you'r only going for audio editing then it should be fine.. :)
I don't do too much with it though.
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