Hey Toby.

Since you want HDMI pass through I think either will work. I personally think the difference in weight between the 805 and the 806 is significant. The 806 is significantly lighter and the internal layout is not as impressive. 

I like the following reviews for both the 805 and 806:

805: http://www.hometheaterhifi.com/volume_14_3/onkyo-tx-sr805-receiver-9-2006-part-1.html

806: http://www.hometheaterhifi.com/receivers/469-a-secrets-receiver-review.html

In reality the 805 has better DACs for music vs. the 806, but the 806 has better video upconversion. Since you don't want the upconversion the 805 is a better bit in my opinion.