Have you thought about a yamaha ysp2500 or similar?
Or maybe a sonos playbar and you could use the play 1 as the rears, or higher up to replicate ceiling speakers
I assume the reason for a small centre is because you want to put it in a cabinet? If so this is far from ideal and you may be better not having a centre at all. For surrounds a pair of bipole or dipole speakers maybe a better option than ceiling speakers.