Look guy's, the best place to get a Car-Kit for any manufacturer is Security World, speak to Liz and she will be able to advise what's best.
I've just had a kit fitted for a Nokia 6310i, hard wired as they say, which automatically mutes the Lexus stereo, but you adjust the volume through the phone and not the stereo.
Up until now they had problems with feedback, but it works a treat. They use their own looms, they have a guy that has been in the industry since year dot, and designed these these leads especially for all Lexus models.
They don't recommend the Bluetooth kits though as they are a bit tetchy, stick to the the Bluetooth headsets, I have one too, and they work perfectly.
They will come to you and fit too.
Cheers........Sharaz