can you do it? sure.
will it screw up your sound? maybe, but they're both 2.5 inch cones, so mabye not.
power difference? looks like the system is sending 60 watts to both.
the difference in wattage looks like what the speakers can handle, max, with 10% THD
but that's not what they're actually getting. They're getting 60 watts to both fronts and surrounds. (maybe)
If you keep the volume moderate, you shouldn't fry anything, if that's your worry. Give it a try , and judge the 'lesser sound quality' for yourself. Personally, I cant see it improving anything. If you must have smaller fronts... it wont cost anything to try it out.
Just from those specs... it doesn't look like you're getting huge sound anyway. If you're happy with it, that's really all that matters... just don't ever listen to better, and you'll never feel like they're lacking.