Since you intend to use USB port on your notebook computer, bare in mind that USB interface requires CPU as central controller and most likely the USB bus has to be shared among various devices connected to it. Thus it will not be ideal with the shared bandwidth and restricted bit resolution imposed by USB standard. If your notebook computer is equipped with PCMCIA (old) or Express Card (new) slot, perhaps a dedicated sound card with SPDIF coaxial/optical outputs will be better than the USB port. I know that Creative Technology do offer such sound card for notebook computers. Take note that any on-board amplifier and its analog outputs are not needed in this case as only digital audio outputs of the sound card will be used. USB port can only be the last but not first resort as far as digital audio interface is concerned.
I decided to buy Denon D5000 instead of D2000 because of D2000's loose bass after extensive audition and comparison between these two headphones. So make sure you have audition before making purchase as headphone reviews are always subjective to individual preferences of reviewers. Though you have budget constraint right now, but it will be worthwhile to buy the right gear in the beginning than spend more money/effort to upgrade later on. Perhaps you can achieve what you want by buying one right item at a time rather than buying all wrong items at once. It will take longer to achieve want you want but with less regret/spending in the long run.
Just my two cents after learning through painful/wasteful experience.
Edited by littletree76 - 5/9/10 at 5:20pm