The weakest part of listening to an iPod using any of these gizmos, or through your main system for that matter, is that you are limited to the performance of the DAC in the iPod, which leaves something to be desired, in my experience, when compared to playing a digital feed through a decent convertor/DAC (you'll need a computer for that - you can't do it via an iPod as far as I know - if so someone tell me how). For $4k you could buy yourself a very respectable system, especially buying used gear. If you're going to listen to amplified iPod music, the only excuse I can think of is portability I suppose. I brought my iPod into my hotel rooms on some recent travels and played it through Swan M200's, which beat watching cable TV, and cost a whole lot less than $4K for the speakers. If it's at home, why bother....use a better rig if you've got four grand to play with. Fer'chrissake!
Marco