Isn't it, the power of the w7 is great. Ticks me off when people say that it'* not a good sub, they just don't know what their talking about.

Red tops are meant to be used in replacement of the stock battery.
Yellow tops are meant to run accesories such as an extra stereo battery dedicated only to the system. This is what I have and have had no problem and voltage reads 14.7 always.

Realisticly getting a beefed Alternator is a good Idea. I'm eventually going to get one. Interestingly though, my installer advised me that more amp alt is still no guarntee that the stereo will be 100 power. So you get more amps, that doesn't guarntee any more voltage. Recomended me into getting one of those Voltage Regulators from Jacobs Electonics.