Jerry,
My 561 tells me it locks on 44.1. The AIFF files are the "same" as WAF so I presume I am getting bit for bit digital audio. I cannot hear a difference when compared to a 506.20
As for controlling it, either a touchscreen or for that matter, S-Video or composite output on a TV screen with a wireless KB will do the trick.
You can fit 2 x 250Gig drives in the G5 so that's roughly 720 CD's in full format on the Mac. You can always add external firewire drives to add storage. They come cheap.
You can also control your Meridian gear through the serial port using a USB>serial adapter. If it's just Prev, Next, Play Stop etc. I'd be more than willing to write an app for you.
The Harmony WiFi TCP/IP to infrared box adds new possibilities. One could use a palm pilot or iPaq to control your gear RF based throughout the entire home.
richard