Power Issues

 1.I'm mounting Rockford Fosgate FNQ 3614 6.5" components  in the existing door mount. 6.5 mid and-a 1" tweeter and was going to mount the same on the top of the deck directly behind the seats in the space available inside the rollbar mounts. I am going to use a Rockford Fosgate 851X 4 ch amp for those speakers. I originally intended to use headrest speakers but think it will sound better like this. This part is relatively straightforward I think. Plenty of power with speakers rated to handle it.

2. I originally intended using ONE Rockford Fosgate 3X2 12" DVC RFR3112 sub with a 1000bd Rockford Fosgate amp.I was told that this would have to be run at 4 ohms-1ohm not recommended. That would give me a 500w max, which I was told would seriously underdrive the sub. That means if I understand it correctly that I would need a 2nd sub to be able to get to the 2ohm load. I admit it doesn't make sense to me. I would think that if I run two subs at 2ohms from a 1000 watt amp, each sub is getting 500w. If I run 1 sub at 4ohms that sub is getting 500w. Can someone please clarify this and explain what the downside in sound and volume would be with the 4ohm configuration and how marked an improvement in sound running a 2nd sub at 2ohms would be in comparison. I'm most interested in sound quality, but obviously want volume as well, at least to balance with the front speaker setup.

3. My final question- I'm not sure  whether the battery/alternator in my Miata is built for this type of load. I bought an  Alumapro 5 Farad Cap to help with this. Will the cap be enough? Or do I need to look at adding a separate battery for the amps? Or is there another solution to make sure I have enough power and don't drain my car?

Any advice will be greatly appreciated.    

2.  If you added a second sub, you are correct, you could wire to acheive a 2 ohm load.  By wiring your amp at two ohms you would be doubling your power, but splitting it two ways.  So you would be sending 500 W to two subs, rather then just one.  I've always found better sound quality at higher loads, but then you get less power.  If you have the power run it at higher loads, if you don't run it at a lower load.  In your case, I would hook it up at four ohms, and see how it sounds.  If it's not enough sound for you, think about adding a second sub or a bigger amp.

3.  I think you'll be okay with the setup you have.  But once again, hook it up and see how your car handles it.  If your having problems consider adding a battery or rebuilding your alternator.  But don't worry about that until you test it out.