Hi Guys, jumping in here...
I've just upgraded to a Onyo PR
-SC5507 and am planning to add a set of speakers to go to 9.2. I'm currently running a 7.2 setup with Polk RT5000 (RT3000p mains, CS1000p center, FX1000 side surrounds and an extra pair of RT3000p upper satellites as rear surrounds.) I run a pair of SVS PB12/Plus-2's for subs. The 5507 does a nice job of room correction for both subs, BTW.
I'm considering adding a pair of Polk speakers for height, and have a choice to make. I already own and can use either a pair of Polk RT55i's, or a pair of Polk R1's. Here's my question, "How much frequency response does the height channel need?" I know more is better, but wider freq response means bigger speakers. The R1's are fairly small, and have a freq response from 65Hz to 20kHz with 5.25" driver. The RT55's are a lot larger, with a freq response of 35HZ to 25kHz. The R1's would be much easier to install, and if they have enough freq response to cover most of the audio signal sent to them, they'd be my choice.
I run a 7 x 200wpc amp for the existing speakers, but would probably use a smaller amp for the heights - somewhere around 75wpc. I could, however, run the heights on two of the 200wpc channels and use the smaller amp for rear surrounds. Obviously the larger speakers would benefit from more power, but again, if the signal is not there, why overkill?