My brother is having issues with dialog and I'm looking for a few suggestions.

His setup:

VP180
M60s
4 QS8s
SVS PB13 Ultra
NAD T765

He's having trouble hearing dialog, particularly during movies. With the system set up and calibrated properly, dialog seems quiet and hard to hear, but when the bullets start flying, the overall volume in the room gets quite loud. I can't turn up the overall system volume to hear voices because action scenes get overly loud.

He's resorted to turning up the center volume. He's at +4 now. We calibrated it to +2 and even that was a tiny bit higher than the measurements showed. At +4, the sound stage collapses to the center channel.

His seating positions are off-center a few feet since he wanted two love seats so I am wondering if I'm getting too much combing from the VP180. It's particularly hard to hear female voices.

Or I was wondering if I should enable Dynamic Range Compression in order to bring up the low volume scenes, and knock down the loud scenes. I'm not even sure if his NAD can do that since it tends to leave out extras that nobody uses.