You should be fine if you use your head and ears. If something starts to soud bad, turn it down.
Speakers only draw as much power as they need to play at a certain volume.
Generally, you use much less than five watts for fairly loud listening in a home environment. The rest of that power is rarely used, and is kept in reserve for for an occasional peak, which most speaker can easily absorb.
Bass can be a different issue. I assume you're running a subwoofer with those, right? Those are nice speakers but aren't really made to pump out big, deep bass that a larger speaker can. If you try to force it out of them by throwing more and more power at 'em, they might not like it very much and your concerns may be justified.
So, if you start to hear strange noises, someting is complaining and you should turn it down now, not later. Oh, you'll want to set your speakers to "small" in the receiver setup.
