In no one was I trying to insult your recommendation for him to get a G4.

I have nothing but respect for the time you took to type out that list of gear and pricing.
I have used both Mac and PC for years (only hand built PC's) and it has just been from my experience that I've found you can get a better bang for the buck with a properly spec'd PC. Building a PC is incredibly easy and for under $1000, he could build one that would literally destroy an $800 mhz G4. And are you serious about you're comment about noise?!? I'm not sure running a vaccuum cleaner while tracking would be any noisier than a G4!

A quick solid PC recommendation:
Asus A7N8X deluxe (NForce 2 chipset)
Athlon Barton core 2500+
1 Gig of RAM
120 gig Western Digital HD
Win XP
He could base his entire recording setup around this... and I would suggest Sonar 3 for recording. Incredible bang for the buck.
But IMHO, I think it would be foolish for anyone to spend $10,000 on a studio that hasn't been completely thought out. I not sure fldrummer has an understanding of the learning curve he's up against. I would suggest he buys a computer first and some audio software with a decent multiple channel audiocard (if that's what he wants) and learn from there. Everything (as far as what additional gear he needs) will slowly fall into place from there.
Generally, I will research any ONE piece of gear for a few weeks before I will purchase it, so to me... spending $10,000 at once seems foolish. I'm almost willing to guarantee you will regret half you're purchases.
At any rate...
I wish you all the luck.
take care
ls