Trey - I think Steve is just pointing out that the sound difference you'll notice in most formats when going from 5.1 to 7.1 is minimal. (and I agree, though I do have 7 channels also)
If you wanted a new receiver for reasons other than the decoding (say you wanted the nice GUI, network streaming, or some other feature that you could only get in the Denon 3808 or any other replacement receiver). If that was the case, you might get more bang for your buck by getting a new receiver first.
However, if you're upgrading solely for the ability to play 7 channels from the HD-audio formats, then I agree, you'd be better off upgrading to the 7.1 sound first, due to the limitations you mentioned with the HD formats.
It's a personal choice, just realize that the differences of matrixing 5.1 sound to the extra 2 channels is pretty subtle. If you ever do 7-channel stereo listening though, the difference is a bit more apparent as the QS8s do really sound nice from all angles of the room when running in that mode.
Jason
