Will someone please explain the difference between the XKR-S vs XKR-175 vs XKR-75?

I know that the XKR-S is for European markets and the XKR-75 is for US markets. I am not sure about the XKR-175 or the performance and features of each.

 

To the best of my knowledge the XKR-S was a 2009 UK model with the 4.2 liter supercharged engine with 420 hp. The XKR175 is a US/Canada model with 510 hp. Sales are limited to 175 cars. The XKR75 is a UK model with 530 hp. Sales are limited to 75 cars. All three have a top speed of 174 mph instead of the normal 155 mph. I believe all three have similar appearance and suspension packages but someone who is an XKR owner or expert might have additional information.

Hope this helps,

Mike