you can do the same in JS if you have such simple particles as well (ie rendering by just writing a few bytes). http://mrdoob.com/lab/javascript/strangeattractor/ does 300k as well (though it's borked right now since he has to update his stats code).

here's another fast one in webgl: http://iacopoapps.appspot.com/hopalongwebgl/ reading the source, it has 280000 particles.