A receiver that doesn't have HDMI doesn't have Dolby Volume. I would try redoing your setup with the center speaker removed. I had some NHT speakers (Classic Three) a while ago, and the L/R were significantly better performers than the center. Depending on your room and seating position you may find that a phantom center is better than an inferior center.
Center Speaker Suggestions??
I have a 5.1 system with all NHT speakers driven by a Denon receiver. The center channel (which does the yeoman's work when playing Blu-Ray,) is unintelligible. When using my Denon wireless headphones, the sound is glorious - very easy to understand dialogue... so I'm thinking something is not right with my NHT midrange speaker. Does anyone have a suggestion?