If you don't absolutely need the networking features and iPhone control app, I would HIGHLY recommend the RX-V667 (last year's model) over the RX-V671 (current equivalent model). The amplifier section, HDMI switching, and high-definition audio decoding are essentially the same among both models. To maintain the same price point but add networking features, Yamaha removed the 8-channel multichannel input and 7.2 channel pre-amp outputs from the V671. If you think you will ever want to use external amps, the V671 is not for you (while its predecessor, the V667, is more future-proof in this regard).
On Amazon, the V667 is $350 currently while the V671 is $500. For someone who doesn't need internet connectivity in a receiver, the $150 savings is a no-brainer.