Actually, no. You don't really need a high-output alternator nor another battery.
You can probably use an Infinity Reference amp. Go to Crutchfield.com and peruse their amps.
EDIT: This amp should work. It says "mono" but it has 2 input channels for left and right speakers.
http://www.crutchfield.com/S-cOmVlIi...20&I=108R1600A
FYI - You don't have to turn the gain ("input level") up all the way. That's just stupid anyway. If you only turn the gain up 1/2 way you still get correct wattage to your subs without overpowering them and limiting the usage (ie. having them blow out faster). I suggest you spend the money and get 4ga wiring as recommended. And if you feel like you need the extra juice then run a 1.0 farad capacitor. If you don't know what that is then you probably should get somebody to install all of this stuff for you.
GL