I would say almost tripling rated will be pretty hard on them. Where are you crossing them over? I would consider stepping back the gain a little bit and feed them untill you start to hear them being overworked. Any unwanted sounds will let you know when they have too much.
you can run a 400 watt amp to them no problem just set the gain to where they only see a little bit above their rated rms. Dont set it for the full 400 or even 300 rms. They wont like it.