I had a GROM system on my rx400h. It works very fine, accept bluetooth, USB, audio connexion, mp3, flac and lossless files.
I added USB and jack plugs in the central armrest
your Lexus rx accepts it as a second CD player. All steering wheel command are available .
http://www.ebay.co.uk/itm/Grom-Audio-USB-iPhone-Android-Integration-kit-for-LEXUS-IS-RX-ES-GS-GX-LS-TOY1-/182083399719?hash=item2a65043027:g:v~MAAOSwwE5WZaef