An amplifier usually designed as Class AB; meaning during lower wattage usage (usually 10 watts on demand, up to its limits.
A Class A amp is always running full bore, regardless of what is asked of it, the extra wattage will turn to heat. There is no A to B switching, thus less distortion.
So, Class A or AB has less to do with how much power it can produce, rather it discribes how the amp is designed. Class A is less efficient, hot, but can sound very nice and warm. But,there are good sounding amps using either designs.100 watts of Class A is no more power than 100 watts of AB.
As for the speaker asking for "up to" ( I assume max) of 250W...it is probably telling you not to drive 250 watts into it, which is very very loud. Unless, you are really into head banging music, I would not worry. The amp and the speaker should be a great combo. Enjoy.