Paul
Unfortunately I think you have posted in the wrong forum. The processors talked about in this forum are pre-amp processors rather than pure video processors (which from your post is what I assume that you want).
You need to look at this forum:
http://www.avforums.com/forums/video-scalers-video-processing-progressive-scan/
I am not an expert at all on video processors but have been following the pure video processor forum for a while as I have a similar interest to you in optimising my video performance. As with all AV kit, there appears to be a huge price range. However, the starter price for a reasonable processor appears to be significantly greater than for other AV kit.
This product is apparently good for the price:
http://www.royjowetthomecinema.co.uk...-Hot-Deal.html
and is discussed here:
Themescene HD3000 - any major downside?
However, the forum members on that forum are probably in a much better position to advise.