I'd be looking at the less expensive Denon vs the Marantz since they are for all intents and purposes, the same units, or look at a comparable Onkyo. Whether you go up to 7.1 depends a lot on the size of your room . There isn't so much info on those extra channels vs 5.1,...personally I think you'd get more benefit from upgrading your centre channel to a VP160 or 180, and maybe considering adding a second sub(later) if you have room, before adding more surrounds on the speaker side of things.

Half of communication is listening. You can't listen with your mouth.