Question on amps, if anyone can help?

Just to clarify a couple of things.  First, the BP1200.1 has two sets of RCA inputs so that you can get bass even if you have your head unit faded to the front or to the rear.  If you always keep the fade in the middle though then you can hook up only one set of the RCAs and it will sound the same.

The amp has 3 dials for adjusting stuff:  input level ("gain") adjustment, bass boost adjustment, and low-pass filter frequency adjustment.  The LPF can be set as low as 32 Hz or as high as 320 Hz, and you will need to play around with it a bit to see what sounds best in your vehicle.

This amplifier does NOT have preamp outputs, so if you're going to be using a 4-channel amplifier in addition to the JBL amp you'll either need a 4-channel amp that has preamp outputs, or a head unit with 3 sets of preamp outputs (front, rear, sub).  If the head unit only has one set of outputs then you'll be better off using a crossover to direct the appropriate frequencies to the appropriate amplifier.  This also applies if you have a factory head unit and will be using a line output converter to get a single set of RCA outputs.

Technically the BP1200.1 can use high-level inputs and you could send the RCAs from the head unit to the 4-channel amplifier, but I always recommend using RCA type connections whenever possible, to give you the best sound quality and the highest S/N ratio.  What kind of head unit is in the vehicle right now?

150 watts per channel @  4 ohms RMS??????  That is a LOT of power you're talking about and I honestly don't know of any amps out there that will give you 150 watts RMS per channel when they're run at just 4 ohms.  A lot of them will do it at 2 ohms but not 4.

anyways, I saw from another post that your vehicle is a ford truck.  I'm pretty sure they have fairly large alternators in them so you might be okay as is. I'd say first try out the system and see how it sounds and see whether or not your lights dim at all with the system turned up, especially during a long loud bass note.

If the lights dim at the very beginning of the note but return to their original brightness before the note has ended, a capacitor would probably work pretty well for your situation.  It would mean that your alternator is capable of producing the required amount of current, but it's just slow to react to the additional demand.  The capacitor would provide energy to the amplifier during the split second that it takes for the alternator to react.  Make sure you try this test both with the truck parked/idling, and when you're out on the highway, just for comparison sake.

However, if during that long bass note your lights dim and stay dim until after the note is over, then most likely a high output alternator is a better way to go.  A capacitor would just make the alternator work harder and over time this can possibly lead to premature alternator failure.

Admittedly HO alternators are always gonna be better solutions than capacitors in either of the two above scenarios, but they are also much more expensive solutions and are not necessary for every vehicle.

And obviously if your lights don't dim at all even without a capacitor or HO alternator, then you don't need even need to do anything to it!

This was for a 97 F-150 right?? If thats right then you cant use 6X9's anyway, you will be using either 6X8's or 5X7's. An amp that i have ordered recently and am awaiting it to be shipped is this one from Crutchfield http://www.crutchfield.com/cgi-bin/S-m7imu7zfJ66/ProdView.asp?s=0&c=3&g=120&I=235USB4085&o=m&a=1&cc=01&avf=Y.

It is an 85X4 and by the specs is a real good, clean amp.

I am curious how you are going to install your 2 12's cause my wife drives the same truck. Are you going to take out the back seat??