[quote user="Aewheros"]
Here's the deal. I've got a couple of Sennheiser hd595 and a Pro-Ject Head Box II. They are connected to an old Creative Soundblaster Live! soundcard, which is propably worse than many integrated soundcards manufactured today. Obviously, the headphones and the amp are much better than the soundcard.
Should I upgrade right away without hesitation or doesn't it matter much? How important is the source for the overall audio experience?
[/quote]Considering the quality of your headphones and seeing that you got some decent amplification, I'd say it's defenitely worth it to upgrade on the source side.There are quite a few options here, much of which has already been extensively discussed here on the forum. Best search for external dac or soundcard in the searchbar on this forum. Assuming that you've got a pc as a source, I would advice you to:
1-rip your music cds with Exact Audio Copy (takes a while to set up well, but certainly worth the effort)
2-use an EXTERNAL DAC (like the beresford) or soundcard/midi device (EMU, Tascam and the like). See http://www.stereo.de/index.php?id=197&L=0 www.thecomputeraudiophile.com or http://www.aqvox.de/Asio-USB-Audio-installation-e.htm for setup with Win XP. Action 2 will give you the quickest results without to much hassle. Using EAC and high quality files (lossless) is only an icing on the cake.