just cause your sub is rated for 250-500 doesnt mean you cant use the Memphis....it would probably be better for the sub...
you just need to properly set the gains on the amp...
you would be getting more power and less noise throughout .....if you had the gains on the amp low you would actually be causing it less stress...
I have had 360 watts on speakers rated for 100 and they sounded great...you just cant crank the gain or you will blow them.....
think about that before you go and buy a 200watt amp that your going to overdrive trying to make it loud...your going to blow that sub like that fron distortion....