15 watts & 94 db eff. speakers: how loud?

With a Trends 15 watt t-amp and small tekton design speakers, with 6 inch fostex 167es, rated @ about 94db, i can get about 93-4 db sustained average (@ 1 meter per speaker) with peaks around 96-7. It sounds perfectly good, nice and clean, no treble break up, nothing different than @lower volumes, only louder.

BUT, at ANY higher volume the amp starts to clip. One hears of many such rigs with even lower wattage 300Bs and such, which is why i wanted the efficiency of the speaker (as well as its single driver design). I've never really used a solid state, much less digital amp before. I'm wondering, is this the nature of hard clipping in digital amps, to begin before there is any real noticeable distortion or is something wrong with the amp? Is this generally how solid state clips? How loud should speakers of this efficiency go with this many t-watts? Finally, how many watts do I need to have some more head room (let's face it, I'm only comfortable with my rig when I know I can accidentally destroy the speakers late one night) : )

Thanks in advance!