It depends on how into good sound you are. If you install a 4 channel amp it will sound considerably better. My nova is the first car I have ever installed an amp into and it makes a huge difference in my opinion. not only do you have more power but also with the crossovers the speakers only get the sound they can reproduce giving them a cleaner sound. You would need to run RCA cables under your carpet from your head unit to the amps. Also your speaker wires would need to run from the amp to the speakers instead of from the head unit to the speakers. If your battery is rear mounted it is easy to get power from it. If your battery is in front you also need to run power under your carpet from your battery to your amp. Good luck and let us know what direction you went.

Depending on your money situation, you could do a few things, I would go with a speaker setup with more than 4 speakers and use an amp, or if money is tight and you don't want to do the amp at this point, have the interior shop run all the wires so that you could easily add one later on. I have taken apart so many interiors to put amps in, it is never fun.

The front speakers are where you really want the quality sound coming from, as they are where the soundstage/imaging come from. The rears are just for fill. This being said, you could run an amp for the fronts, and run the rears on the head unit. I have done this in several cars with great results. If you are thinking about a sub, you can use a four channel amp and run the sub on the amp's rear speaker outputs. These are just a few of many configuration choices that work. No matter what you do, at least run the fronts on a separate amp.

I agree with this comment; it is a sane and reliable way to achieve a stronger front stage and have some rear fill without breaking the bank.

If you already have a multi-channel amplifier, you can typically bridge a pair of the channels to drive a subwoofer system at a higher level. Watch your impedance when bridged- the output devices will run as if working at half the system impedance. You can use the Zmin spec from the system or just take a DCR measurement with an ohm meter and be close enough in most cases. The instruction manual that is included with most amps will cover this adequately.

One other point to mention. Any head unit that does not have an active amplifier built into it will not make more than a few watts- no matter what it says. If the unit has some sort of DC-DC conversion or digital tracking power supply, then you can get marginal gains out of the head unit, but typically it is ohms law all the way and that says you are working on a max swing of 14 volts. Even at a theoretical 100% efficiency, that 'aint much into a 4 ohm impedance. In reality, a head unit with no amplification circuit will swing about 6, maybe 8 volts best case- just doing the math for the 8 volt swing gives you a figure of 16 watts.

It would sure be interesting to take a few head units on the market and test them with an AP or a VP-7723 analyzer to look at power vs. distortion and IM. I know from being on projects using similar amplifier setups for i-Pod docks and things like that, the power vs. distortion and non-linearity is really poor; especially in the days of ultra low cost devices.

Phase