Ned, I don't know a lot about the 6's, but I've heard the same thing - late 635CSi's were in many ways similar to the M6. Where they differed, I believe, is in the engine - the 635 used the basic M30 big six that was also used in the 5 series and 7 series, anywhere from 180-200 hp, whereas the M6 used the 250+ HP engine from the E28 M5, a highly modified, hand-built version of the M30. Remember that the 6 was effectively a 5 coupe, built with the 5 platform (E12/E28) as a base. You might want to check out the following sites for more info: http://www.geocities.com/silbersix/ , and

The 850CSi was a whole different beast than the 850Ci and 840Ci. It met all of the criteria for an M8 - six speed manual, bored out V-12 (5.6 liters, 372 hp), and heavily upgraded suspension. I've also read that the CSi was even assembled by the M-division, rather than on the regular line. I don't know why BMW didn't call it that, I read once that their marketing vision for the 8 series didn't include M cars. There were only a few hundred imported in 94 and 95 (maybe 93?). I got a ride in one once - sweet, and very fast. The owners know what they have; on the downside, they're very expensive to buy, on the upside they've probably all been really well maintained. The other 850's, the Ci's, aren't too far from the situation the early 750s find themselves in, where if something goes drastically wrong with the engine, they may not be worth fixing. The 8's were complex cars, lots of electronics.

Eventually, the www.8coupe.com site should be up in the US, until then www.e31.net gives some good info - Euro site, but lots of US-applicable info.