I have been really impressed with the
Spigen Classic C1 case (the one that was designed to look like the old iMac). It seems to provide great protection and fits my X really well -- to the point I had to go to YouTube to figure out how to get the case off. It is a three piece case -- a TPU gray/silver inner case, and then 2 harder plastic outer pieces that snap together over the TPU. Unlike pretty much any other two piece (top and bottom) case I've had, these 2 pieces, once snapped together on the phone, are basically impossible to get apart (which is why I ended up on YouTube to figure it out).
The case feels very good in the hand, the top "hard" plastic piece has a very grippy and soft texture, the bottom piece is more a traditional "hard" plastic, it feels a bit slick. I suppose you could say it is my backup case -- I use it when I want/need the better protection. My favorite case is still my
Burkley Sturdy Snap On case, I absolutely love the leather used in that case.