Do the new S2000's come with XM radio already? I see in pictures the head unit says "XM Ready"

All I need is a subscription and I am good to go?

 

The head unit is XM ready. The XM tuner is an option. If you have a silver antenna on the rear decklid you will have the tuner.

 

I can't figure out why the S2000 needs that rear deck lid spoiler, while my Element has it built into the same antenna the S has.

The Honda accessory for XM is around $400 I beleive. I would invest that into an XM type headunit and get the mod to allow use of the controls to the left of the wheel. Better sound, less money,and you get a smaller antenna you can "hide" easier on the car.