I have similar rear, front and centre channel speakers from the same manufacturer (Sonus Faber) but couldn't afford the same speakers all around (all though they would fit the room). I have moved from different amps to the same mono-blocks for all speakers. My "matched" speakers don't provide complete uniformity. The different "voice" of the rear speakers is very noticeable, and the centre is very noticeable with music, but not so much with dialogue or sound effects. Moving from different amps from the same manufacturer to the same amps did improve the uniformity a little, but the speakers themselves (and positioning) are the main contributor to their "voice".
In the end I've decided to live with the difference of the different speakers. Currently I mostly listen to 2 channel music, so my main speakers and system are optimised for that. My surround sound is spectacular compared to most other systems, but it could be noticeably improved. Maybe by the time we have a good catalogue of surround sound music I'll be able to afford the same speakers all around