Quest For The Right Mac, g5 vs. g4 vs. imac etc. Options

[cwmiii3]

..depends on what you do and how much you want to spend. yes, i know..and more so than before thanks to reading posts for the last week.

So here' s my question to macmusic users: i'm currently a pc user with a modest starting studio setup (Mbox, PTLE, decent moniters, and at least one half decent mic) who does some home recording of guitar based music and crafted radio production work. In other words, i'm a semi-professional who does everything from layered pop songs to 1/2 four track audio documentary work....and looking to get more serious. my pc laptop just barely meets my needs and, after pulling out my hair trying to run ptle for the past couple months, i've decided to go mac. But which one is for me ?

i've done a fair amount of research on this and to tell the truth, i still can't make up my fri'ggin mind. Money is an issue, but more in the sense of 'should i borrow towards the G5?' The noise factor is also important, mainly because my current computer makes so much of it and it drives me bonkers. Finally, which macs are more audio friendly than others with more i/o's otions?

One final aside: i was all settled on 'buy for the future' approach and had picked the G5 1.8 duall as the best bang for the buck. But then, i talked with a Guitar Center mac studio guy who said i, given my equipment and needs, it was like pairing a Jag with a flat tires. Does the truth hurt? his advice: i should think G4. any suggestions?
thanks,
cwmiii3