dont buy just any amp, buy one that will be compatable with your subs, matching wrms and ohms
for example, im running 2x 500wrms 2+2ohm subs off a monoblock 1600wrms amp, bridged i believe gives me 1ohm at 1200watts, thats 600watts each going into each sub, plenty considering i wont ever give it the beans as its a show install and not performance, below 1ohm i believe causes problems
thats the general gist anyway, lol