I think we may be confusing/conflating two different issues in this thread. I read the original question as applying to a center speaker with an integral subwoofer, not a separate sub altogether. I have four different AV systems, and one of those uses a Definitive Technology CLR 2003 center speaker, which has a built-in subwoofer. Set correctly, it does not induce any boominess or chestiness into male vocals. It does make a big difference on things like explosions/gunfire, giving much greater impact in the center channel. Of course, I also run subwoofers (at least two) in each of the AV systems.
Subwoofer with center channel
Does anyone here use a subwoofer with a center channel? I was watching a Riverside concert dvd today and was surprised by the amount of content being sent to the center channel. My Sonus Faber center speaker sounds good, but I wonder what I might be missing. I have a decent NHT SubTwo I subwoofer that I'm not using. Maybe I should give it a try..