In my honest oppinion if you're going to watch 1080p FullHD Blu-Ray movies (as that's all that produce FullHD, even SkyHD is 720p) then you'll have to look above $400 possible way above.
The issue with cheaper models is that there has been so much 'slimming' down to keep cost down that you really do not benefit from any HD experience. Here
is a HDTV buyers guide which you may find informative.
It cost me £3,999.95 (over $6,400) back in 2006 and is only 720p (1080i) capable. Pioneer - PDP435FDE