I think what nikolausp is getting at is this:
For example: I have all video sources running through my receiver, with a single output from the receiver. I don't have a Darbee, but if I did, it would go between the receiver and the TV.
For any content with a resolution lower than 1080p, I can have the receiver upscale (and de-interlace, if necessary) it to 1080p before it goes to the TV, or I can have the receiver leave the signal as-is, and let the TV do the up conversion.
So, if I had a Darbee, would the end result be better, if these signals were up converted before they reached the Darbee, rather than after?
Nikolausp does not have an upscaling device upstream of his TV, and he is wondering if it would improve the results he gets from his Darbee.