i have a similar set up, avr 235 (had it 2 weeks and love it, except for the manual), paradigm cc 170, 5semk3 and atoms, but with a sub.
the manual pg 20 says the small setting is for satellite spkrs that dont produce sound below 200Hz. so you may lose that range for any speaker set to small.
any opinions on how important that is for center/rears?
i believe other receivers have different criteria for setting large v small, such as onkyo and yammy (which i tried.)
how does your center sound with music? overall i am pleased, but the center can be a tad harsh on some highs, but i think it may be in part due to the cd quality.
right now i have all spkrs set to large with all crossover at 100Hz, but still tweaking.
also, if you use logic 7 for music, which is a nice hk feature, the system will default your center to small when logic 7 is in use.