You can improve this.

I would recommend not using that guitar. Although it is very nice, it's hard to integrate with the other instruments, it stands out too much. A little bit of eq on it would do nicely. Possibly cut some of the high and some treble frequencies. Also, the drum samples have a good concept, but I'd recommend using samples in place of the ones you are currently using. Places like looperman and breakbeatparadise sites will result in very nice quality samples. The background (harmony) synth works well, just some slight light reverb and lower volume will compliment the melody. Same for the choir. The reverb will fill in the space to make a fuller bodied song. (Slayer is good, but on it's own. It never really fits in. Try getting an electric guitar plug-in and throwing your own distortion/effects on it, it will yield nicer results.)

Omfg...

That, was fucking awesome man, more, please more, omfg... :D <3