There are some early reports that the SR MBPs have a lot of (unresolvable) interference over the headphone-out jack. Before I drop the cash on one of these, wouldn't using the optical-out to a headphone amp solve the problem? Apparently, the optical-out's sound quality is flawless, and not subject to the headphone interference. I'd prefer the optical-out solution b/c there's no additional CPU or I/O processing that I'd imagine a USB solution might impose (however, if you have a good USB sound device solution, post it!). Now the question is, do you have any recommendations for such an amp? Also, do you know of any that might be battery powered, since one advantage of a laptop is to break the power-cord tether?