this is what I've heard - hopefully some of it is true and helpful to you!
first - you need to get digital of your pc or laptop. Little effort, alot better than the headphone jack, especially if your media PC is in another room and you're runnign cabling any distance.
* I've been told the digital out of any onboard sound in a PC is as good as you'll get - and investing in a better third party sound card isn't going to help anything. In other words, the zeros and ones do not need the sound card's higher quality componets to become 'better' zeros and ones.
* I've been told that USB 2.0 does not have enough bandwidth to carry a full signal and to avoid the route of a USB sound device. If you're using a laptop, then I guess that directs you to get a PCIMA sound card as the other poster recommented.
Personally I think a laptop should be fine - it's the digital PCMIA sound card doing the work and putting out the signal that matters -as long as the hard drive and processer can keep up, then the laptop itelf should have little effect on the sound quality - I was, in fact, quite happy using a laptop to do just what you're doing - benefit is that you can have the laptop right on top of your audio rack and control playlists etc. right from your living room.
Other thing to consider. If using a PC, think about getting a video card with HDMI out. Then, interconnect your digital sound to this video card - entire video and sound will come through HDMI into reciever - this will allow you to remote control your PC from your LCD panel to control your playlists, - and watch youtube in grand style
Laptop wins for simplicity though, in my opinion. When I had that configuration set up, I played and enjoyed more music than ever before - which is kind of the point!