^^^
fwiw, i use itunes on a mac mini connected directly to the marantz... i've done it the "apple way" for years, first with an airport express and then with an appletv... besides the "apple way", there's many ways of skinning the streaming cat...
however...
since you mention "ipod/iphone", i'm guessing you are an idevice kind of guy (like me)... very shortly (as in 3 days), we should be getting the airplay upgrade... then you will not require a hard drive hooked up to your pre-pro at all, you'll just be able to stream from your iphone or anything that is running itunes...

airplay (assuming correct implementation) really IS gonna be the best thing since sliced bread... a lot of us are waiting quite anxiously for it... there are a LOT of people out there with idevices... imo, this is gonna be a great feature... used in combination with the wizz app and the apple remote app, it's got a lot of "real world usage" possibilities (unlike most "features")...
some answers...
- yes. assuming correct formatting and music files that the avr will recognize.
- either way works. i'd use whichever one has the best user interface.
- 3 part answer:
o cd - yes, easily.
o dvd-a - yes, a bit more difficult
o sacd - no.
- both. as they are "lossless" codecs, neither is of "better quality". "lossless" is exactly that, lossless. what goes in, comes out.
