jingai

Hello, I have a 2010 Mazda MX-5 with the factory Sirius option. I'm considering purchasing either an F90BT or X910BT, but I was wondering if it's possible to use the factory Sirius unit? Or do I need to buy the Pioneer unit? If I need to buy the Pioneer unit, will it work with the OEM antenna, or will I need to run a new antenna? Thanks, jingai