OOC, what do you guys want to know exactly? i can tell you from talking to Bill that there were no real changes to motor structure of the Watkins at any point for the Quantums and Reference Standard series. the possible exceptions would be the Ren and Omega varieties, and also the big IRS I/III/V's. in my experience, upgrading to the brand new black poly cone from the very old black-coated paper cone yielded only a subtle extra tightness in the bass, which one would probably expect, but it wasn't so noticeable that i can't be sure i wasn't imagining things. still, that was reportedly the main motivation in manufacturers moving away from paper cone woofers anyway.
IIRC, Bill mentioned that he designed his new woofers to perform exactly like the old ones, since making subjective "improvements" to the design could reduce drop-in ability.
"RS1b" can probably tell you more of the technical nitty-gritty, as he's made several very informative posts before.