centre speaker

I would like to improve the sound quality on my speaker system in particular w.r.t. voice in movies and classical music, e.g. PROMS on BBC4 My amp is an Onkyo TX-L50. Would exchanging my centre speaker alone help? I have been looking at the Q-Acoustics Concept 3090Ci.

I am planning to replace current audio amp to enable my main stereo speakers (Heybrook Quartets) to take the surround front L & R from Denon 3800 av amp, and replace the centre speaker - currently old Kef 'egg' with a better speaker that will complement the Quartets. Perhaps one with a fabric...