I want to add XM to my 700BT, but I'm not sure which one I need. I know the website says P920XM, but the guy at Best Buy told me the 920XM would work, and from what I've read online it sounds like it would work. Anyone have any idea what the difference is?

I believe they are both the same thing.

This is what Pioneer says for your unit. http://www.pioneerelectronics.com/PUSA/ ... 00BT?tab=C