Receiver running less than 5.1 channels

[MrRoy]

I re-arranged my front room, so I am now closer to my tv, speakers, etc. I haven't connected my surrounds yet (need to run new wire and use banana plugs), so I set my receiver for 3.1 instead of 5.1. The audio sounds noticably better. Is it because of the distance or because of 3 channels instead of 5, so the receiver has more power to push each channel?

Thanks!