As others have mentioned, the best center channel speaker to use with Magnepan mains is a Magnepan center channel. I used to use an Infinity IL 36c center channel speaker with my Maggie 1.6's and 1.7's. That Infinity was a substantial three way speaker with ceramic drivers, that worked very nicely. However, when I switched to a Magnepan CC3 center, the improvement was dramatic. The Magnepan center blends so much better with the Magnepan mains.
What happened to your CC5? That couldn't have been very old.
Main system: Thiel 3.6 L/R speakers, Pair of Velodyne F1500r subs, B&W HTM center, Emotiva and Polk RTi 28 surrounds, Integra DHC 9.9 pre/proc, Pair of Emotiva XPA-1's, Emotiva XPA-5, Threshold SA/4e, pair of Threshold S/200's, Oracle Delphi TT w Magnepan Unitrac 1 arm and Shure V15 - Vmr, Logitech Squeezebox Touch, Oppo BDP 83 optical disc player, Threshold T2 preamp, Denon DR-M44HX cassette, Pioneer CLD-97 Laserdisc. LG PF1500 led projector,Elite 100"tab tension-ed motorized screen.