Alternator

I have 2 batteries in my car for extra accessories (subs, lights, etc.) I'm pretty sure the alternator in there is stock. The front battery keeps losing voltage little by little when the car is runnin. The battery is fine though, it holds a 12 volt load, and the back battery is wired in parallel connection with the front battery so there are double the amps, but still 12 volts. I'm guessing the stock alternator can't pump out enough amps to both batteries...simply because it's stock. I went down to advanced auto and they only knew of 2 alternators which I could put in my car, and I already had the one and the other one wasn't much more powerful. Does anyone know where I can find an aftermarket alternator that I can use in this car, and it'll be powerful enough?

I found a high output alternator (140 amps compared to the 75 amp in now)for a 90-94 non turbo eagle talon on e-bay. Would this not work on my car because it is a turbo or is there no difference?

It will work, but why do you have TWO extra batteries? One should be sufficient. Is the second one hooked into the electrical system at all besides the stereo stuff?

Sorry I meant 2 batteries altogether. One is under the hood basically just for starting purposes and what a normal battery is there for, and the other is in the trunk for the stereo stuff and lights. But your positive that'll work and the plug will still fit with it used to being in a non-turbo and I havin a turbo.

Ok well I found out today that there is a difference between the turbo and non turbo alternators. The turbo has the voltage regulator built in, as opposed to the non-turbo. Does anyone know how to install a voltage regulator, onto an alternator or is that something that needs professionally done? And how much would it cost to do it myself of have someone do it?