I'm also in the same boat and am torn between the Yamaha 663 and the Pioneer 1018. I really like the features and feedback for the Pioneer, but it is kind of ugly. I'll probably take some abuse for saying that but it is part of the purchase decision.
I have been scared away from Onkyo Receivers due to so many complaints of Humming through HDMI and also the very hot operation. I came really close recently to buying the Onkyo 606. For you wanting to use Wii, I would really do some research to find out all the pros and cons of the 2 receivers you are considering.
I am using mine for a Sony HDTV,Sony BluRay, and regular television broadcasts.
The one thing I liked about the Pioneer was that it has a USB port on the front to plug in an IPOD.
Let us know what you decide.