Go for the Onkyo, that's my advice. Their new receivers get praised everywhere.
Onkyo receivers, especially the 905 has one of the best 2-channel sound stage you can get in a receiver (well, without going to the pricey Yamaha Z11
). The Onkyo receiver has a neutral, well balanced sound and has more power than the 4308.
In several side-by-side tests I have read, Onkyo receivers are always coming way ahead of the Denon ones (for comparable prices).
You should also check out the Yamaha RX-V3800 and Pioneer VSX-LX70 or 90. These are very good too
If you only want to watch movies then I would strongly consider the Yamaha RX-V3800 ...