Surround Sound

[tuxify]

I recently purchased some Logitech G51 5.1 Speakers. This is the first set of high quality speakers I have ever owned, and I have never even dealt with surround sound on a PC. I'm using my onboard sound that is on the GIGABYTE P35-DS3L (Realtek ALC888).

I started reading up on surround music, as this is the main reason (with movies in mind as well) I purchased these speakers (I only use headphones for gaming which is the primary use of my computer).
I realized that most MP3 encoding is done in stereo, and not in 5.1 surround sound. This didn't mean much to me, until I actually got the speakers and listened to music.
Don't get me wrong, I love the speakers. Best set of PC speakers I have ever heard. The bass is amazing and the speaker quality is superb. Apparently Logitech put a Matrix system in the control box, where with the matrix off, regular MP3 music that I didn't encode myself only comes from the L and R speaker, as well as the subwoofer. When I turn the matrix setting to music/gaming, it takes the stereo quality music from the L and R speakers, and puts them, in lower quality, to the two rear speakers, and the center speaker.
I haven't really listened to a movie, but seeing as I don't have any quality movie players (VLC is the best one I can find for free) that would be able to play 5.1 surround, I don't think I'll get any better results.
So short of buying every album I listen to now, and every album I plan on listening to in the future, is there any way to be able to listen to music with the full 5.1 surround sound?
Like I said, I'm not very educated with computer audio, so I don't know if there are things I'll have to do to get it to work (ie. get a real sound card).
Sorry for the wall of text. I just really want to get the most out of these speakers.

*EDIT* A couple other things I forgot to mention:
I have the Realtek Audio Manager off, which is the startup program that came with my motherboard.
If I sound really ignorant about this audio stuff correct me please. I'm just trying to learn here.

 

[PunterCam]

I don't quite understand. Yes MP3s are in stereo, but so are CDs, vinyl, cassette, every single music format since 78s in the 1950s. If you want to play music back in 5.1 you have to use this 'matrix' conversion your G51s provide.

Occasionally you'll find a DVD of a live show, and it may have been recorded in 5.1, with the rear channels playing some of the room and crowd, but no album (ok, there have probably been a couple of obscure things recording in 5.1) is ever recording in 5.1.

As for playing movies back, I use VLC with my z5500s, and it sounds great. I don't know if it's using a genuine 5.1 soundtrack or if the unit is doing a conversion, I don't care - it sounds great.

EDIT: I have the same Realtek software running - use it and take advantage of the EQ, you can make these speaker systems sound much fatter at low volumes. Boost the bass a tad and take a couple of DB out at 600-700Hz; these systems do pish mids, do it a favour and take some of it out