I-Mac for computer audio?

To answer your 1st question, you won't have any SQ advantage by choosing an iMac over a mac mini. I have both, and both use the same optical out that causes some to complain about jitter.
I agree, however, with the post that questions your setup at such great lengths. I had this same problem, which is why I eventually settled on buying an older, used mac mini and running it "headless" - i.e., no monitor. Apple has an easy to use screen sharing mode where you can access one computer with another Mac.

If you don't want to go the 2 computer route, then you really should consider using an apple tv or airport express to stream wirelessly. Both of these devices have a digital that bypasses the internal conversion and lets you pass a bit perfect signal to a stand alone DAC. I can tell you from experience that they work great and, assuming you're running a wireless N network with the router positioned within a reasonable distance, you won't have any problems with drop outs. The only downside is you're limited to 16/44, meaning if you want to go high res everything you play will be automically downconverted. There is workaround to this, but it requires that you have an iPad (any generation)and still limits you to 24/96: http://www.benchmarkmedia.com/discuss/feedback/newsletter/2011/06/1/ipad-streams-high-resolution-audio-dac1

I concur with ( Nonoise ) keep the USB cable as short as possible.

I like your plan. The implementation....not sure, as in 40 ft for one thing.

I'll tell you what I'm doing and see if it might work for you.

Using my Wifi: I have a dock (Cambridge iD100) that routs the digital stream of one of my iDevices (Phone,Pad or Touch) to a DAC for use in my main system. Been doing that for about a year. Very happy with the results.

A few weeks ago I got an Arcam drDock. It will do what the iD100 does but it also has analog outs using its own internal DAC (Burr-Brown I believe). Using it right now with an iPad (Pandora One) "hardwired" to a CJ ART pre/XA30.5/SF Guarneri system. Again, very happy with the sound.

If that doesn't resonate with you then maybe the Airport Express route. If your system has good resolution, you'd probably want to use the AE's audio out with a mini Toslink adapter into the DAC of your choice that would be "hardwired" into your system.

Either way(s), I think some form of wireless will be needed.

If you use a Mac Mini late 2009 model, you can use a 16-foot USB cable with no impact on SQ. Buy it on ebay. Late model Minis have cable/USB port issues and do not sound as good IME.

If you want the best off-the-shelf SQ at 40 feet, then go with Logitech Touch wireless. It can be reclocked for even better SQ. Not as good as wired USB though.

Steve N.
Empirical Audio

Audioengr,

Thanks for the info re: late 2009 Mac Mini and that it can use longer lengths of USB. If I can't move to a better place and decide to go forward, that makes it easier.

All the best,
Nonoise