TV Upscaling processor and/or Upscaling set top boxes

[Solid79]

In a nutshell:

I have a Virgin Media SD set top box
I am looking to buy either Sony X3000 or Samsung F86
Will I benefit from an upscaling set top box or will the LCD TV processing bypass and superscede it in quality?

Answers on a postcard please Depending on the answer I MAY be tempted into persuading Virgin Media to give me a free V+ set top box!

Thank you in advance

Solid