Maui Mana

I'm setting up my family room with a home theater system and looking to Klipsch for the speakers. The room is about 18 FT x 18 FT, and the ceiling is 10 FT. The back of the room is actually open to the other spaces comprising the main living area. And I'm also on a bit of a budget so I don't necessarily want to over do the power capacity, simply looking for a balanced HT speaker setup that matches the size of the space. The surround and 'back' surround speakers are already in place and are Speakercraft AIM832 ceiling speakers (and I know 'ceiling' speakers aren't ideal but the interior architecture didn't really accommodate wall or floor standing surrounds). Also, my sub would be the R-120SW as it seems to be an obvious one to go with in my situation. And the receiver will likely be at the Yamaha TSR-7850 level (hopefully it would be enough to drive the selected setup). So I'm really looking for advice for the following: 1) given the size of the space and existing speakers, could I get away with using R-625FA's for the fronts, or would the RP-280FA's be a notably better fit? (question is driven mainly by budget concerns) 2) is the R-625FA's most suitably paired with the RP-250C center speaker, or would they go better with the RP-450C? I'd appreciated any advice on this as I'm close to pulling the trigger on a setup. Thanks...