Have you tried C.P.E. Bach? He has some stunningly good and beautiful music. Among the most adventurous and expressive is a set of six symphonies for string orchestra (W. 182), the early, highly experimental "Prussian Sonatas" (keyboard) (W. 48), and a number of really good keyboard concertos. Among the best is one in D minor (W. 23) that is, IMO, more interesting than most of Mozart's. If you aren't impressed with the latter, he is probably not your cup of tea.
There are also trio sonatas, lots of chamber music involving flute, and oodles of choral music.