The best detectors are currently the Valentine 1, Escort 9500ci, Escort Redline and Bel STi-R+. The V1 and Redline are "windshield mount" and the 9500ci and STi-R+ are "remote" mount. All are stealth (undetectable by a radar detector detector) except the V1; important if you drive in VA or DC. They are the most sensitive detectors available. You've spent plenty on your BMW. Don't skimp and get a cheap detector because the cheaper ones do not perform as well. There is lots more to say about this topic so do some Internet research.
Also, don't forget about a laser jammer if it is allowed in states where you drive. And in the end, it is not the detector that will save you from a ticket but the way you drive and your attention while driving. Detectors are just a supplement.
I've been assimilated. 6MT/ZPP/18"/PS extended.