Depends what kind of processor you are talking about... if you mean a HT processor, then maybe not... or maybe... depending on how good the chip is in the processor versus the source.
If you mean a video processor, then the answer is that it will most likely improve pretty much every signal you through at it (much better technology than what you will have in most sources or TV/projectors). I'm using my DVDO VP30 for all my processing (digital TV, DVD, HD recorder etc.) plus HDMI switching and extracting the digital signal as coaxial to my PRE/PRO. The improvement is obvious to anyone!
If you mean a video processor, then the answer is that it will most likely improve pretty much every signal you through at it (much better technology than what you will have in most sources or TV/projectors). I'm using my DVDO VP30 for all my processing (digital TV, DVD, HD recorder etc.) plus HDMI switching and extracting the digital signal as coaxial to my PRE/PRO. The improvement is obvious to anyone!