First off. you don't really "need" an upconverting DVD player.
Every TV up-converts all incoming signals into it's native resolution internally.
By using an up-converting DVD player, you're betting that it's upconversion circuitry will be better than that of the TV's internal circuitry. And that's at best a 50/50 proposition.
FWIW, I don't notice much of a difference, if any, when using my up-converting Tosh DVD player into my Tosh LCD.
As for the picture stretching/cropping, every DVD handles this differently. Personally, I'm not one for a stretched, distorted or cropped picture. I much prefer the native format whereby on a 4:3 pic I have black bars on the side. Likewise, any pic that 's not 16:9 will most likely have thin bars on the top and bottom. At least what I do see is in the correct perspective and I get all the picture.
Buy, we pays our money and we takes our choice.