rjc: Well, given the pretty high compliance I'd assume you're runnng the ADC on a pretty light arm, for which I'd deem an AT150Sa not quite as attractive. And no, you're not really missing out, 'cause carts haven't really got that much better ever since the mid 80s anymore, and most of the progress in the MM/MI realm had already been reached around the mid 70s, so that most of the better carts from back then are still pretty competitive now. That being said, it's of course always possible that you might find a model that's more to your liking or fits better to your turntable and/or system environment, be that an old or a new one.
Greetings from Munich!
Manfred / lini