A couple of points...
Trek is not evil for buying Klein or saving Klein from bankruptcy or whatever, just for turning Klein into Trek. While there were nice frames from Klein produced after Trek ownership began, the entry level Trek-Kleins aren't much more than Treks. Why pay inflated VRC coin for that? Why not just buy a Fisher Montare for 50 bucks? People avoid "post Trek" Kleins because of that dilution of the brand.
The best way to avoid a blah blah Trek-Klein is to avoid anything with unsmoothed weld work. Regardless of pre or post Trek production date, proper Kleins should have smooth welds, period.
While some would argue that the Palomino is not a proper Klein, it is worlds better than the Mantra and Adept! Best to not have a full suspension Klein of any type though. What's the point?
Not all Adroits have goofy little fibers reinforcing the tubes. Some are simply Attitudes with holes in the dropouts and/or fatter tubes.
The Rascal and the Top Gun are essentially the same thing, But here's a little nugget passed over by most Klein fans...The Fervor is also the same frame...albeit with an inferior paint job to the typical Klein slatherings. Similarly, the Mountain Klein and Pinnacle are also kissing cousins. Geometry for the Pinnacle is more lazy and pedestrian than the Rascal/Attitude, though...so be warned. SO...if the Klein paint mythos isn't your bag and you want to jump on the vintage Klein bandwagon without spending a boat load of dough?...buy a Fervor with a trashed paint job and polish it!
Early Kleins have long seat tube extensions. Use a 410 post and avoid the cracking gremlin.
Zip Grip is garbage.
Klein/Cannondale comparisons are apples to oranges and are off target by a long shot. I have a 1993 Cannondale Beast and a 1990 Klein Rascal, and they are very different bikes. The Cannondale is a fun bike, but compared to the Klein, it is a pile of garbage.
Personally... and this part is r
eally just my opinion... I wouldn't own anything but a Rascal or a first gen MC1 Attitude or Adroit, and even then I prefer the Rascal. Rascals were Attitudes with normal head tubes. They are stiff as hell, very light, very quick and for a talented, balanced and agile rider, offer a rider experience unlike anything else.
Your mileage may vary!