I recently purchased some Polk speakers and had a question. I have the 70s for mains, 60s for surround, and just bought two pairs of the 40s, one of which is for surround back. I was going to use the other pair on channel B as an extension in another room; however, I think I'd like to use one pair as centers.

I am using a Pioneer VSX-1022 for my amplifier, and it is rated at:

Power Output per Channel (20Hz-20kHz, 0.08%THD@8ohm): 80W
Power Output per Channel (1kHz@8ohm): 110W
Power Output per Channel (1kHz@6ohm): 140W

My confusion comes when looking at the ratings on the speakers.

The 70s are 20-275W , 8 Ohm each
The 60s are 20-200W , 8 Ohm each
The 40s are 20-125W , 8 Ohm but sold in pairs.

Can I use both speakers that come with the 40s, or would hooking two of them in parallel to the center channel change the impedance to 4 Ohm, thus below the guaranteed speaker impedance of 6 Ohm listed in the receiver specifications?

Thank you for the help!