I gotcha, I thought it was a hum in the output whereas it was coming from your speakers, not from the unit itself.
You really wanna pacify that pefectionist in you? Change out the soundworks center for something the BA VR line...

I used an MC500 a few years ago w/an Infinity Interude setup and never realized how off the panning from left to right was until I got a matching center. It's a nice speaker, it just didn't mesh as well as I'd thought it would.
Depending on your music to movies ratio, it might not be terribly important, but then again... -TD
ps
Really, I'm not trying to spend
all your money...