BudgetAudiophile

I have an Onkyo TX-8020 audio receiver and three sets of bookshelf speakers. The receiver has terminals for two sets of speakers. Is there a way that I can wire all three sets into the two sets of terminals? Perhaps with two pairs wired in parallel or serial?

One speaker set rated for 6 ohms and the two other sets are rated to 8 ohms. I want to run speakers in my small house for the kitchen, office, and living room. Speaker impedance math is so over my head. Any help would be appreciated. I just don't want to burn out my receiver. This is all cludged together from garage sale finds and family giveaways.

The receiver power output is rated as: 180 W (3 Ω, Front) 160 W (4 Ω, Front) 100 W (8 Ω, Front)

The speakers sets are rated at: The two Dayton sets - 40W, 8 Ω Pioneer set - 80w, 6 Ω