Finnissy is underrated.
These days a good composer can't get known unless they achieve some kind of subculture notoriety, like John Zorn, whose sub-standard free jazz noodlings and dadaist nonsense reel in lots of fans and allows them to stumble over his lesser known (and far better) chamber compositions.
Interesting that you should mention Zorn -- I'm a great fan of Naked City's first album. I've heard a "bit" of his classical music but haven't really investigated much into it. What would you recommend? The string quartets maybe?