With regard to the advisability of a recon DVDO Edge
1. Confirm your warranty and non-defective policy returns policy with any vendor you use. You don't want to be stuck with a restocking charge if you run into a compatability problem
2. Post and ask both about recons and the specific vendor in the thread I linked to in post #7 in this thread.
With regards to the Onkyo's, be aware that the excessive heat generation that resulted in fires in the xx5's continues in the xx6's. Another issue is Onkyo's widely reported lack of customer support. Read up on them first!
The reason I mentioned the Denon 2309 was to give you a relatively inexpensive receiver upgrade option. Another such option would be the Yamaha 863. If the video processing options at this level are not enough for you, it would take at least going to last year's Yamaha 3800 (still a current model) to keep what you have audio-wise and add HDMI processing.
Since you already have the 4600, and are aware of the desireability of having separate video processing, the DVDO is the way I'd go.