help this newbie ?, help Options

hey all...

i could use some advice. i'm very new to the Mac world (6 months or so) and have limited knowledge of tech-speak. with that, here's my Q...

i own a roland vs-880 expanded, which has served me well for 4 years. however, the cost of storage is killing me, as is the slow transfer of material to 250 zip discs. the small screen is no picnic either! i have the effects card in the VS 880, which isn't too bad. i don't do any work with midi or sequencers. all in all, the VS ain't bad.

now i own a 4 or 500 mhz iMac (200 some odd megs of memory, 10 gig hard drive), and have downloaded the free version of pro tools. i also have a cheap casio that i'd like to use as a midi-controller for absynth. can i use pro tools/iMac and the VS ? should i just make the switch to pro tools ? i realize that i need a way to input audio into the iMac, and some have suggested the iMic, or more expensive options like an edirol or motu 828. a Mac dealer that is highly regarded here in New York told me that the iMic was cheap and way too noisy.

long story short--is it worth it with a G3 processor ? is it too expensive to get it up and running ? should i wait til i buy a G4 (or G5) a couple years down the road ? and should i fork out the cash for OSX ? or is OS 9 just fine for this ?

thanks for all your help--feel free to contact me directly

james