I agree with there is no appreciable sonic improvement or degredation going onboard or outboard with the drives containing the files.
Wireless G allows sufficient through put of packets so it should be good enough to allow seamless playback. Interruptions can occur, but these are normally caused by outside factors affecting the frequency 'G' operates at. Vista as well using it's Windows default packet sending settings can be an issue for streaming wireless info, but it's an easy fix.... another thread I posted here shows exactly how to overcome slow feeds/seek and interruptions or 'drop outs'.
I can stream DVD's I've place onto a NAS drive via G to my laptop without interruption of either the audio or video stream, and I did not compress The DVD's orig info... it/they were ripped at 1:1.
There are threads here which expand upon which way is better, wireless or wired, if you look into the discussions search engine. I seem to recall the use of ethernet wire as being better.... I think.
I've tried both ways but not both ways with the exact same PC OS. Just XP Pro SP3 and Vista SP2.
Reportedly Macs have an easier time of it sonically, than do PCs. As with your own audio rig though, theres more than just a couple things which will come into play that can and will affect the audio output from your personal confuser and the overall SQ.
Enjoy.