How do I run 2 pairs of tower speakers.

I have a pair of Klipsch rf3’s and a sub on my denon avr-1908. I got a pair of rf7’s and want to add it to the set up. This is strictly for audio and not movies. My neighbor gave me the receiver for free so I’m working with what I have until I upgrade to an amp/pre amp. Can I plug the rf7’s into the other front output? And are there newer receivers that support this in case I want to buy one with pre outs in the future? Most receivers I see now only have 2 front channels not 4 like this one.