Well that sucks that all youve got is 250, and to answer your question about 2200 watts to your hdc15, that thing will eat up the 2200 watts and burp some LOUD *** bass right back at you
u have 0/1 wire? Big 3? if u do then i say GO FOR IT
if u dont, i still say GO FOR IT, but make sure u get that wiring right, and u can always add a Batt to the back, that alt should supply enough juice to both batts