Can you run a 6.1 receiver with only 5 speakers (plus sub) leaving the center rear empty? I'm thinking about using a leapfrog type upgrade path and replacing my aging DPL Sony receiver with the Denon 2802. I purchased a Polk system several years ago, but can't afford to make the jump with receiver and full 6.1 speaker upgrades at the same time. If I'm planning on making this receiver purchase last 4-5 years, what are the benefits of biting the bullet and going with the 3802? Thanks!