--Not much to say about the Cello Concerto. I like it.
--Op. 9 should be voted on as a set. Its the first of his four-movement quartet sets that follow the symphony movement pattern. I think Op. 1 might technically be the more seminal set (if its indeed the 1760s) but I'm not as interested in the divertimento style.
-- Symphonies. 6-8 are colorful favorites. Not sure about #9, for another early one, I'd pick #13 with its tight opening movement beautiful cello concerto slow movement and jupiter-like finale. #21 & #22 were composed back to back. #21 came first and is actually the more "interesting" work but its hard to argue with the gorgeous simplicity of the english horn & horn dialogue of the latter. #34 is proto-Sturm & Drang... I think 1765 is more accurate... its the bridge between the sonata da chiesa of #21/#22 and the full sturm & drang of #49. I don't know if I'd vote for it by itself but its a fascinating transition piece. #31 has the horns and the great variation-finale. I really like #30 with its short festive opening and flute parts in the second two movements. #39, #49 and #26 are full Sturm & Drang (#26 is misnumbered, it belongs with those two). #48 is one of my favorites.
--I've read good things about the Stabat Mater. Haven't read anything about the Missa Cellensis. Stabat Mater's are a bit too glum for me and I'm not really into masses -- its always the same script and its not really a good "story", its a mass :-) -- but masses do very well in these games so I'll let others be the judge.
--Wagenseil's seminal symphonies are from the previous decade. A 1764 piece by him is going to sound anachronistic. Does he have a decent keyboard concerto from the 1760s?
--CPE: Here's a chronological list of CPEBach pieces:
I think his more seminal pieces are from the 40s and 50s but maybe some gems from the 60s can be found. We all know the Solfeggietto from 1766 but I don't know if a 2 minute piano earworm is nomination-worthy. Cello Concertos, Flute Concerto in G, Keyboard Concerto in D minor... all from the 40s and 50s. Bummer.
--JCBach has to have some works here. He was the court composer for George III at this time. Same with Abel.
--Boccherini's early chamber works (single digit opuses) were extremely influential -- a lot like Haydn's Opp. 1&2. They inspired other composers to write quartets and quintets without continuo. But like Haydn, I think its the post-1770 works that we usually hear from him. Any Boccherini fans out there?
--Rameau & Telemann lived into the 1760s. Any very late works by them that are nom-worthy?