Might also check to see if your receiver is not stuck in some 5 channel stereo mode. In this mode, all your speakers would be sent sound to play but they would equally get all the same sounds. There would be no separation between whats supposed to be surround sounds and what was supposed to stay up front. Would definitely take the fun out of a movie but some like it for music.
Also, you might experiment with setting your surrounds to small instead of large. Definitely leave your mains set to large until you get a sub, but it can't hurt just to experiment with the others.
