Not sure if this is feasible for you, unless you are comfortable with getting your hands dirty, but I decided to forgo the use of a 3rd party library and write

Not sure if this is feasible for you, unless you are comfortable with getting your hands dirty, but I decided to forgo the use of a 3rd party library and write the WebGL code myself for my latest project. Other folks mentioned geometry merging, and for me, that has been the single biggest performance booster on my current project. We were hitting a wall with some models that had 30,000 individual objects (several million verts, 10 million indices). But since we were writing the WebGL ourselves, I just added a bit of code to batch up all the objects into as big a bucket as WebGL could handle (up to 65k verts per draw call), thereby reducing the number of draw calls (drawElements). For our larger models, we went from 1100 ms per frame, down to 1-5ms per frame. We've done other things as well, but none had so large an impact as merging the geometry into larger chunks. But I can't speak to doing that in Three.js, since I didn't use it. But you should easily be able to handle the geometry you've got at 60 fps.