Denon options
With the additional power and headroom of the 3805, you wont need to use the bi-amp option to deliver similar power to your speakers. If the prices are comparable, go for the 3805 which has a beefier power supply, better amplifier, and more features. Since the 2106 is a brand new model, you are probably paying close to retail, vs. a significant discount on last years 3805.