Personally, I don't see a tremendous improvement using an upscaling DVD player. All I've seen require you to use an HDMI cable form the DVD to the TV but, honestly, by using a component cable with my current DVD player and letting the TV do the dirty work, I can't tell much of a difference, if any.
I suggest you try your current DVD player first. Then try one of the new upscaling players, but keep your return options open.
FWIW, my "gold standard" is the big blue guy's fur in Monster's Inc.
Of course, if you're thinking of one of the HD formats, that's another story.