$2,666??? GOOD LORD!
Why not build a dual processor x86 box, where things will be WAY cheaper, and you can do same as everything with one of those as you could do with that G5 box?
Okay, beggers can't be choosers, but let's examine your config, and see where changes could be made to save money:
• Dual 1.8GHz PowerPC G5
Again, why G5's? Athlon XP's, or Athlon64's would be WAY cheaper. Heck, depending on the traffic you're getting, you might be able to do for a P3 or something.
• 512MB DDR400 SDRAM (PC3200) - 2x256
• 2x250GB Serial ATA - 7200rpm
• NVIDIA GeForce FX 5200 Ultra w/64MB DDR SDRAM
Do you really need this beefy of a video card? If this thing's a server, go get a used PCI 8MB or 16MB video card, because you will not need that much video memory or power if you're not doing any graphics processing.
• 56k V.92 internal modem
Are you going to be serving over dialup? If not, you don't need this. You could choose to omit it if building your own x86 box.
• 8x SuperDrive (DVD-R/CD-RW)
I'll give you this, since you've got 500GB of space on this box.
• PCI-X Gigabit Ethernet Card
Do you have a Gigabit LAN? If you're running this over broadband, a 10Mbit card would do. Besides, you can pick up a 10/100Mbit card for $10, easy.
• Apple Keyboard & Apple Mouse - U.S. English
Again, if this is a server, these are almost pointless. Get a $10 keyboard, and a $10 mouse. Since it's a server, you can just borrow one from another machine temporarily. From there, since you're running Linux, you can just SSH or VNC into it to do all of your adminstration.
• YellowDog Linux - U.S. English
Retail box? Grab Fedora Core from a retailer, or just download it. Later on, donate some money to the developers. Your options really open up when running x86. Debian or FreeBSD, anyone?
If you're going to ask people for money to get a server, at least make it look like you're trying to be judicious. I've got enough money right now to buy the box you're after, but I still would be picking up a P3, or lower spec, if I were going to build a webserver.