I have the RhinoSkin case and have never had a problem with scratches or anything. I think it is a great case if you are looking for a hard sided case. It adds some bulk to the x50v so be sure you really need a hard case before you get it. I got mine through Dell when I got my x50v, but you can get one
HERE form AximCases for $34. They also have a buch of others if you have not seen them already.
As for the screen protector go with the big name ones.
BoxWave and
Brando are good ones. I have the Boxwave Crystal Clear and really like it.
Can't really comment on the rest. Good Luck~
Adam