The Pioneer VSX-917 pales in comparison the the RX-V661's performance. If Dave intends to upgrade to an HD Disc format in the future it would be in his best interest to get the RX-V661.
The Pioneer only passes HDMI, nothing else. The Yamaha will upconvert over HDMI, do 8 channel LPCM (for HD-DVD and Blu-ray), DSD (for SACD).
The Pioneer has the same amplifier that the 816 has, which isn't much in comparison to the Yamaha RX-V661.
The Pioneer doesn't have preouts for all channels, the Yamaha does.
The Yamaha has more advanced setup features and flexibility.
Lastly, the Yamaha has more connectivity.
This is the Pioneer.
The reason I am pushing the Yamaha so hard is because I think Dave will be really happy with this unit, and it should satisfy his needs now and in the near future. I am not trying to break anyones glass, just trying to suggest the best possible solution for Dave.
Good luck Dave.