How loud can I 'safely' play my Dynaudio Focus 140

Hello folks,

A random question from a total newbie. Did a quick search here but, still had some lingering questions so here goes.

Just recently traded in a pair of Dynaudio Audience 42s for a pair of Focus 140s and was wondering how loud I can crank these guys up without stressing them out. I don't have a fancy powerful amp but, I tend to listen to music at a fairly loud level and was curious as to if that listening style hurts the speakers at all. To clarify, when I mean loud, it isn't to the point where the sound gets distorted and I can't hear myself think so I'm assuming everything is cool but, I wanted to see what others think.

What are the rules of thumb when it comes to taking care of speakers? Are there any tell tale signs to look out for in order to avoid frying a tweeter or blowing a woofer out aside from obvious sonic distortions?

On a random side note, if anybody has any suggestions on a great amp to match the Focus 140s with please let me know!

Just started working on putting together a stereo system and so far loving every minute of it!

Thanks!!