I just purchased a Yamaha HTR-5750 receiver and I plan to purchase the following Polk Audio speakers to connect to this receiver:
Fronts: LSi7 (4 ohm)
Center: LSiC (4 ohms)
Rears: FXi3 (8 ohms)

My concern here is that the impedance select switch on the back of the HTR-5750 indicates the receiver can drive 4 ohm speakers on the front channels, but only 6 ohm speakers on the center and rear channels. This seems to be the true for all of the HTR series as well as the comparable RX-V series Yamaha receivers. I do not plan on playing the system extremely loud, so I don't think this configuration will be a problem, but I'd like to make sure. Any input is is appreciated.