Maybe a good Oberon leather cover would help as that little original Sony cover just isn't enough. (all sorts of colors and designs available oberondesign.com) They make them for the Sony 505s and 700's and 600s. Square Trade also sells insurance with accident protection for one time accident with a $50-60 deductible. I bought that for my Kindle2 and the DX. I got the Oberon cover for my Kindle DX, as it is almost an extra 1/2 inch bigger around than the reader. Very good protection for drops, as I have done a few. Not sure about smashing it in with a car door though.
I am not affiliated with Oberon.