I wouldnt go with in celling speakers, they seriously compromise sound quality in exchange for the ultimate WAF.
Your going to be pretty limited as far as the L&R channel go since those speakers look pretty narrow and are already flush with the TV and sides of the entertainment center.
As far as the center goes, you could always just save money and not get one. I use to have a 7.2 system in a dedicated HT and now have a HT in another room but I only have 2 large towers and 2 large subs. Honestly i dont miss my center channel that much. So long as you get decent L&R channels they will produce a phantom center. When I demo my system to people they proclaim at how good my "TV speakers" sound, they are surprised to learn that my TV speakers arent on, all that center sound is coming from my L&R channels.
Main System: SVS Ultra Towers - 15" custom ported subwoofer - SVS PB-1000 - Yamaha RX-A740 Aventage
Computer System: Carnagie Acoustics CSB-1 - 12' Onkyo sealed subwoofer - Pioneer VSX-92 THX
Other speakers owned or auditioned: Aperion T6 - Ascend CBM-170 - Energy RC-10 - Wharfdale 10.1 - Arx A1b