For the laptop, the best cost-effective "soundcard" option is get a USB soundcard. When I am home, I connect my laptop to the Creative Sound Blaster X-Fi HD USB sound "card" and DAC. It's pretty good and cheap, but not very portable. When I travel, I use Sound Blaster X-Fi Go! I am actually surprised how good these two devices sound, specially the Go!.
As for headphones, you would be surprised how well a cheap set of headphones like Sennheiser PX100-II sound. I used to think that Koss PortaPro are the best "budget" audiophile headphones, but Sennheisers are clearly a little better in every respect. Midrange? About the same. Sennheiser highs are a little crisper though. As for bass, PortaPros seem to have a bit too much of it. The PX100's have just the right amount of bass and it sounds tight.