I compared my VP150 with an M2 for center channel duties. There was a noticeable improvement (to me, in my room) with a vertical center channel over the VP150. You might want to give an M2 or M22 a try for center duties if you have the space. Keep in mind I have the in on wall versions, and the improvement was enough for me to go through the effort to cut, patch and paint my drywall for the speaker switch.

For the sake of convenience, no matter the manufacturer, small centre channels are always a compromise and because of the design there is the added issue of an unwanted boost in the 300-500HZ range which gives the human voice, depending on placement, an unnatural sound. The vertical designs like the M2, although small, are more even across the frequency range, hence, a more natural sound from the human voice. Like has been said many times before, although not often practical, the ideal set-up is the same identical speakers across the L/C/R.

The larger centres like the 180 and 160 with the bigger drivers and bigger boxes eliminate a lot of the problems that exist with their smaller cousins by adding considerably to the frequency range and as a result, generally don't require that extra volume boost either.

Unless I am not able to listen to a movie at normal levels due to sleeping kids etc. but usually I don't boost the center.

I still boost my 180 center, just like my previous 150. Audyssey has it set to -10dB and the l/r around -6dB, so I bump it up to equal or a bit more.

I run my VP160 about 3 db over the mains. I've tried it matched and didn't like it.