Favorite Center??

A used Aerial CC3B. Just sold mine for $700. Too late. :-)
.

Centers are best matched with the rest of the system so that will also be an issue as you shop for a center. I've been impressed with the Monitor Audio Silver's (haven't heard the reference Golds) and Paradigm Reference speakers. The sound is very different with the Silvers being a bit brighter. Both are good.

The BG Corp 220dx is a great center channel. Very crisp and distinct. Voices sound very natural and airy. It is also one of the largest center channels out there. You can probably get one used under a grand.

The Dali Suite C 0.8. This can be had for around 500.00 and its sound is clean, articulate and full. Plus it looks good.

If you're an audiophile or in the least bit picky, you're asking a question that you should not be asking. If you don't match the center speaker with your mains, you're going to run into the very good chance of a bad situation.

Think about a vehicle panning from the left through the center and on to the right. If that doesn't make you realize the potential of the problem, it doesn't matter what speaker you use. In fact, you can just use your TV speakers.