Thanks Ronnie. I wasn't aware of the Duo, but it's not going to be on my shopping list. The Radiance is, and will continue to be, my primary investment in video processing.
Integration of the Edge is pretty straightforward because it has auto-on and auto-off features, so it come on and off with my SkyHD box. I may end up sending component to the Edge for SD and HDMI to the Radiance for HD, but we'll see. If I want HDMI for both SD and HD, I have a little more automation to do (to get Edge to output different things for SD and HD), but it's doable.
I'm not sure if I'm going to keep the Edge long term; I felt a "need" to evaluate whether or not PReP was worth it for me and that is questionable in light of the amount of SD material I view these days. Unfortunately, the PSU is dying on my Thomson SkyHD box (known issue; I've a repair kit on the way) and it's having all kinds of picture quality effects which means that critical evaluation is difficult.