One of my Greek professors (who was trained in Germany) quoted Kühner-Gerth on a regular basis. It's about as standard in Germany as Smyth is here, and is somewhat longer and presumably more thorough (I haven't worked with it much at all). It also dates from around the same time as Smyth, so you may encounter some of the same frustrations I suspect you're struggling with in Smyth -- i.e., the Victorian style, the condensed and sometimes rather cryptic explanations, certain assumptions made on the basis of Greek and Latin knowledge being far more widespread than it is now, etc.
Perseus seems to have put at least part of it online: http://www.perseus.tufts.edu/hopper/tex ... irect=true
Schwyzer's Griechische Grammatik
is similar in scope. It's (slightly) more recent.
There's a guide to various reference books here which you might find helpful:http://people.duke.edu/~wj25/Bibliograp ... ogica.html