Help with my sound system !!?

So i have this 15inch cerwin vega stroker 2400watts 1200rms, my car has the stock alternator and the biggest battery that would fit in the car(not a yellow or red top) but i used to have a performance teknique amp that was 500rms ,now i wanna upgrade to the HIFONICS HFi1500D amp, before my car would be fine for two weeks then the car would start dying on me and stuff to the car started happening (check engine light, no accerleration ect..) but after charging the battery over night all the problems would go away,, now im on a budget and i would like to know the best solution to solve the car dying problem thanks for your help! =)