Most people bump up their center speaker a few dB for just the reason you suggest. Have you tried that?

That said, more speakers is almost always better! I was running dual M22s for centers for a while and really liked the results. They have since been relegated to the bedroom system, since it was overkill for my HT room.

I started out with nothing & I've still got most of it left
M60 VP160 QS8 EP350
M22 VP100
Algonquins