I can't comment on the video part of your question, but I've been using an maudio 2496. I had that card recommended to me by a professional musician who raved about its sound, and I can easily tell the difference between it and the HD sound on the ASUS mobo in my Linus machine. I found one on eBay for about $85 as I recall. It's PCI, and so should run in your G5. OSX software is readily available on the maudio web site. YMMV. - Michael B. in Cincinnati