New To Mac. Need Help, newbie looking for info on used computer Options

i have many questions here. please bear with me.

i am a Windows user currently. i plan on, in the next few months, purchasing a Mac and getting rid of some of my music hardware. complete upgrade.

here is my plan: i am shopping around on ebay for a used Mac G4. hopefully 500Mhz. dual processors would be ideal, but more expensive. hard drive size not a big deal as i can upgrade/add new drives easily. memory, hmm... hoping for nothing lower than 256MB. 512MB would be nice, and more would be better.

what are opinions on operating systems? os 9? os X?
if the computer i buy has no system installed, how expensive/difficult will it be to install one?

is processor speed a big deal? what if i can only find 350Mhz? and what about memory? how expensive/easy is that to purchase and install?

and i just read a thread on hard drive speed. any comments on that? is it that important for music production?

once i get this computer, i plan on using MOTU Digital Performer with various plug-ins and left-over hardware. and then i wonder: what is VST? then i will need a sound card, which brings up another question:

where do i find info on sound cards? any suggestions? is usb the way to go? firewire? what is "audiowire"? can i get a card that is internal, so i don't have to mess with usb/firewire?

any info is appreciated. thanks for your patience.
semblance

[holli]

Just a point about the dual 500's -they rule! i bought one of the first machines off the production line and it has run absolutely rock solid for the best part of two years now, just as soon as I got rid of protools hardware and changed to motu! They rule also. Some early versions of 9.2 were a bit buggy, I stick to 9.1 for now but only because I've yet to have a break from work to risk the overhall. By all accounts, the latest 9.2 is just fine. Some people have reported the newer quicksilver machines to be a little tempermental with certain PCI hardware -check manufacturers for compatibility before you buy.

Processor speed does matter and so does getting as much ram as possible for serious audio work. The golden rule when buying a system is don't get what you think you need, get the best you can afford. It will ultimately save you time and money.

With a dual500 and the internal 7200 ata drive you can comfortably run 64 tracks of audio. I'm just about to try logic5 and see if it will squeeze a few more. DP should allow more too.

I reackon I'll get another year of service from the g4, using the UAD cards to beef it up a bit. If you're starting out, you may be comforted to know that my dual500 has been the heart of a busy studio, scored two films, two albums, numerous mastering sessions and smaller projects etc etc. and also run almost the entire Siedlachek (never do figure out how to spell it) orchestra from ram (900meg), playable in real time -and I've rarely had to bounce until late in the project -just the way it should be.

Good luck! You'll wonder how you ever managed before!