Home Theater amp and speaker setup questions?

Hey, I have a few questions about amp and speaker set up. I have a Harman Kardon AVR- 135 reciever. I have 5 speakers, Front (L&R), Surrounds (L&R), a center, and a powered subwoofer. When I turn on my reciever and try cranking it past -21, it goes into protection. I think I've figured out the problem, the front and surrounds are EACH 8 ohms. My reciever specs are Front (L & R) 40 Watts per channel @ <0.07% THD, 20Hz – 20kHz into 8 ohms, and surrounds 40 Watts per channel @ <0.07% THD, 20Hz – 20kHz into 8 ohms. So I have 2 fronts that are 8 ohms each, and two surrounds that are 8 ohms, so how would I wire the speakers so the amp doesnt over load. Also if I wire them that way, will the speaker quality change? like if i wire the two fronts together, will it effect sound quality because both speakers will be plugged into one channel (L or R). http://www.harmankardon.com/specifications.aspx?cat=REC&ser=&prod=AVR%20135&sType=H