Quality headphone playback on a notebook computer?


I'm in the market for a new notebook PC, and I want something capable of high-quality music playback, through headphones... In my (somewhat limited) experience, CD playback sounds like crap when run through the built-in headphone outputs of notebook computers. (Apple Powerbook G4, Sony VIAO) Even marginal-quality MP3s played on my inexpensive iRiver MP3 player, put the notebook's CD playback to shame.

Are there any notebooks out there with acceptably good built-in headphone outputs? If not, what are the best options for headphone users? PCMCIA cards? Portable, external, USB sound cards or DACs (that don't require an AC outlet)?

I'm interested in CD, MP3, and DVD playback. Would an external DAC (like the "Waveterminal U24" that I've read about on this forum) prohibit playback of compressed music (MP3s), DVDs, video games, system sounds, or any other computer audio that I might use?

Right now, I'm considering the 'Soundblaster Audigy2 Z5' PCMCIA card. But, I'm somewhat biased against Creative, so I'd prefer to go with another option if there are better (affordable) alternatives. I'm looking for something that DOES NOT plug in to the wall, but can run off laptop battery power, and still provide enough juice to adequately power my headphones. (Sennheiser HD650, and Sony MDR-EX71SL earbuds)

Any help, advice, or recommendations will be greatly appreciated! Thanks.
listen_hear
One way may be to get the Grado battery powered headphone amp. I sometimes run my grado's direct from my Mac G4 laptop, and think it sounds fine. True, not as good as the ipod, and not nearly as good as with the amp, but I wouldn't say it sounds like crap at all. First off, if you're listening to compressed files, then they're going to sound like crap anyway (if we're talking mp3, not losless or something like that). Keep in mind that anything that most peripherals will draw power off your laptop, which will eat away at the battery if you're working away from an outlet (which I assume you are given that you don't want anything that plugs in). If that's the case, then I think there are a number of battery powered headphones amps, and you might want to do some reasearch on headroom, or one of the other forums.

Good Luck
Try the M-audio sound card and any one of many portable amps that you read lots about on http://www.head-fi.org. They have an entire forum devoted to computer-based audio and another on headphone amps. SR-71 by Ray Samuels is one portable by a guy with excellent rep for customer support AND some real audio cred (rave review of sota phono stage in current S'phile, FWIW).
Try a Headroom amp or Dac. I have Total Airhead and it is amazing. They also make a BitHead, Total BitHead and portable DAC just for your type of application.

http://www.headphone.com/products/headphone-amps/