I agree that Ckorody's post was a good one. I almost hate to interfere... but, Howard, yes, you would be able to control volume from iTunes running on the downstairs computer. And that's regardless of whether you have AXpress (I would assume same holds true for SB) or a laptop feeding your CDP/DAC. (Actually, AX probably isn't an option by itself since its digital out is optical and I assume your digital in is S/PDIF.)
If you go with a hard drive in your audio room upstairs and you intend to use it while you're listening there, be sure it's quiet enough not to annoy you.
There are several ways using iTunes to wirelessly serve up music files under the control of a remote computer. Probably the most obvious is using iTunes' music sharing feature. With music sharing, in my experience dropouts are truly rare. Budrew, are you using music sharing?
If you go with a hard drive in your audio room upstairs and you intend to use it while you're listening there, be sure it's quiet enough not to annoy you.
There are several ways using iTunes to wirelessly serve up music files under the control of a remote computer. Probably the most obvious is using iTunes' music sharing feature. With music sharing, in my experience dropouts are truly rare. Budrew, are you using music sharing?