Best Audio Interface for Apple G5 Computer?

I am just wanting to get my feet wet in setting up a music server. To start out I just purchased a Apple G5 Computer. I currently have a Lite DAC with a optical and coaxial interface. I have 3 questions:

(1) To get the best sound should I use the optical out or FireWire out on the Apple G5?

(2) If the recommendation is to go with the fireWire output, what would be the best recommendation for a interface to go from the FireWire to SPDIF? If possible I would like to get an interface for $300 or less (would be willing to find something used on ebay or Audiogon)

(3) Is the new Mac Mini that much better than the Apple G5 in establishing a music server.

Thanks for your help as I am trying to learn about creating a music server.
Get started with a M2Tech Hiface USB-SPDIF converter and feed your LiteDAC. With your system you can begin to experience internet radio stations and your music library through iTunes. See if you like it and go from there. The next step would be a Mac Mini which would be marginally better. You should rip your CDs to a separate drive for storage and another drive for back up. It goes up from there. Check out Computeraudiophile for details. Firewire will limit you to the types of DACs you can use and may not be available in the distant future. Most of all, don't pay attention to all the esoteric and detailed pathways, but enjoy the availablility of all your music library. You can always advance from there. The possibilities are endless. I use a 2009 Mac mini with separate USB drives in RAID configuration plus separate off-site storage running the M2Tech hiface USB-BNC interface to an Eastern Electric DAC BNC input. It is the evolution of music. Enjoy and have fun!
If you're just getting your feet wet, then use the optical out built into the G5. Use it with a decent quality glass optical cable. I use G5s and think they are better than Minis just because they are more flexible regarding connecting hardware. I really don't know if one sounds better than the other. A note of caution with G5s, they don't have the Intel processors and some newer audio software is not backward compatible. It's a trend that will increase over time.
Onhwy61 is correct. The optical output is good and as long as your DAC can handle any jitter issues is a great start. There are many good glass optical cables for good prices. They are high quality polished glass, multi-fiber, and inexpensive. A great way to start. I haven't looked back! I only play CDs when I want to start an album immediately, a rare occurrence.
Tgrisham and Onhwy61 -Thank you for your comments they are very helpful. Have either of you used Amarra or Pure Music software and if so what are your comments regarding these programs.

I also assume from your comments that the audio quality from FireWire, USB or Optical should not make that much difference.

Again, thanks for responding to my questions as I am learning more about digital audio.
I also assume from your comments that the audio quality from FireWire, USB or Optical should not make that much difference.
Don't make that assumption.
"Don't make that assumption."

IME, the connection is as(more) important as the DAC chips or filters. In other words, I think the connection makes a big difference- depends somewhat upon the DAC though.

I would seriously consider moving into a more modern computer. I do not recall about Amarra or PM, but many of the new player programs will not run under OS 10.5 which is the limit of the G5. On my system, the player programs are very different from each other. More so than say, interconnects for the most part, unless one is particularly bad.