The only thing I know about the iscan units is from user feedback on a few sites......and it seems mixed from major difference to zero improvement. My 42" HD (1024X768) display converts all incoming signals to its native rate of 770p (not 720 and I have no idea why...just it's scaler circuitry) I have the older Denon 2900 and tried it S-video interlaced; component interlaced and component progressive. The latter was noticeably the best PQ. My HD cable box offers 720p or 1080i modes over its DVI output and I found the 1080i gave me the best picture (letting the TV scale to its native rate)...you'd think it'd be the other way around.
720p being closer to the native rate. You may find that the iscan gives the best results NOT scaling to the native rate too.
I'm assuming that the DVDO people will let you return the unit if it doesn't meet your expectations.....for that kind of $$$, I'd hope so. I really doubt that it's going to improve the areas (black level, etc) that seem to disappoint you. ISF calibration might help, but the present technology just doesn't seem to be as advanced (contrast, black levels, etc) as the good old CRT. I sincerely wish you luck with your efforts and would be interested if they succeed.
Mort (who's always looking for ways to improve his own stuff)