The best sq will typically be when all three front speakers are identical and placed symetrically in the room.
Agreed, as close to identical as possible which means the three front speakers should be from the same manufacturer otherwise the tonality will be weird and distracting. When all three front speakers are close to the same then the front soundstage will be seamless and dialog can move left to right without changing timbre although most of the time dialog is locked front and center.
My center speaker and L&R speakers use separate amps, sometimes I forget to turn on the L&R amp and watch an entire movie with just the center speaker and never notice. I have a 7.1.4 setup so there is a lot of sound in the room. The importance of a center speaker that can handle both dialog and soundtrack at theater level volume can't be overstated.
Back to your question: Best Center Speaker?
I use a Salk HT2C. The Seas W18 with the magnesium cone is fast with zero distortion and will go louder than you will ever listen. The RAAL tweeter is a perfect match with unsurpassed clarity without any harshness. The cabinet is sealed so the speaker doesn't have any male voice chestyness that can happen with a poorly designed ported speaker. A port is unnecessary because center speakers are rolled off at 100 Hz, deep bass can be more of a hindrance than an asset. The downside of all this perfection is the HT2C's sensitivity is 88dB, a high powered amp is a necessity. I use a rare 3-channel Van Alstine amp that has 120 watts per channel, the other two channels are used for the surrounds.
https://www.salksound.com/model.php?model=Veracity+HT2C$1995.00

My L&R speakers are the Salk HT2-TL that use the exact same Seas and RAAL drivers.
Salk has other center speakers both above and below your budget. Best to call them and to talk about your goals, room size, and current speakers so you get the best match.