It is even worse
.
John, do you own the Pioneer Kuro PDP-4280HD 42 inch Plasma Screen?
This model has a native resolution of 1024x768. This is no HD resolution.
For a proper upscaling without double processing you need either 1280x720 (720i/p) which no TV set has or 1920x1080 (1080i/p) from the more expensive panels.
I am sorry but your TV will (back)-scale any input to its native resolution.
Whatever good job your Denon will do will be downgraded by the downscaling of the TV.
Best will be to use the de-interlacer of the Denon and send a 576p (PAL) or 480p (NTSC) signal. Maybe the smaller Denons have an 'auto' mode? Then this will be your best option.