I'd second what Chess and Ken said. Proper setup/calibration can make all the difference in the world.
You'll also find posts here from owners wondering why their center sounds so quiet, particularly with dialog. The dynamic range on many newer DVDs is such that there's a huge difference between, say, a conversation and an explosion. It can be a little annoying, but many receivers offer a "night mode" where a mild compressor kicks in and evens the volume differences a bit. I'm sure your Sony has something similar. I'd focus on the setup variables first, though.
