I've the newest PREMIUM car kit. It supports / can choose between rSAP - UHV. It should be compatible with all BT Phones.....
... Sadly, no support to use them in combination. I had a thread about this in the beginning of the N900 coming out, this being a nokia phone, I would have hoped they would at least support their own protocols... sadly no.... Bad call Nokia. Don't build carkits with protocols no one supports (except some symbian implementations which where often broken too)..... ...]