I need some advice on High End Car Audio...

I was asked by a friend to figure out what would be a good system to replace the awful standard BMW sound in an older X5. I live in NYC and don't drive anymore, but I remember Wes Phillips had a column a few years back in Stereophile that focused on High End Car audio. Does anyone have any ideas, links or reliable car audio dealers. Most of them sort of remind me of a sale Saturday at J&R Music World...

Regards,
Jody