Urban,
I have my PC hooked up to my Denon AVR-1700 receiver via an optical connection (AOpen AW744Pro soundcard) and some home-built reference quality bookshelfs.  You can go even a lot higher quality than you have now.  Go to a high-end audio store, you will instantly be hooked.  I've been hooked since I was 15 (8 years ago now) and would never turn back. 

  Audio is so fun because it's limitless and a great rewarding hobby.
DIY speakers were my latest endeavor and I plan to build 5 more of them and purchase a subwoofer from 
SVS Subwoofers in the near future.  Over the weekend, I picked up a 
Denon AVR-3801 from a website and I will HOPEFULLY get it next week.
The possibilities go on from here, I have even more i want beyond this but those are my initial wants/desires.
dm