Ok so I just called Kenwood and wanted to make some information public for those of you who have the KDC-225MR head unit. This is stock in my 05 LSV. These are the WIRED remotes that will work with your head unit....

KCA-RC50MR (2009 model remote)
KCA-RC60MR (2010 model remote)

The KCA-RC900MR you might be able to find, but it is no longer being produced and will also work with this head unit.

Cheers.