Bel Canto Mono Options for Center Channel

Since upgrading my main speakers to Verity Audio's I feel my center (Kef 204c) has fallen behind a bit. A new center is not in the cards (the Verity is $18,000, and I like my Kef), so I upgraded cabling (went to Transparent Ultra and ae24e).

I am also considering upgradin amplification. I am currently using a Bel Canto M300, and could consider going to the M500 or the M1000 (not the MKII), if a single unit shows up used. Would this worthwhile or am I wasting my time here? I don't need the extra power, but in particular the M500 is supposed to be better sounding? Should I look for the M500 or the M1000?
M1000 is the same as the REF 1000 MkII. If you feel your power is sufficient, and this is an HT application, moving up is probably not cost effective. I have the Ref1000 MkII and I love them, but they are in my main 2 ch rig.
There's a single bel canto ref100 mkII for sale on audiogon.