audio advice

I am currently running 4 polk db651 speakers and kenwood deck. I would like to add a sub and amp. Looking for advice on which amp to power the speakers and sub. Looking at the polk audio 8" sub. Going with the 8" because I have the old speaker holes from the factory under the dash. Can I mount the amp in that location with the sub or will the vibration damage the amp? I will eventually add some tower speakers and another amp so maybe I should mount the amp in the engine compartment.

One more thing. Can I use 1 amp to run the 4 speakers and sub? I would like an amp that is easy on the battery (if possible). Suggestions?

You would need a 5 channel amp to run speakers and a sub. Polk 1100.5 would do. JL HD 900.5 is more expensive, but would be easier on the battery.

As for the amp location, I don't think you'd have too much flex issues with a Polk 8" sub...although, I'd mount elsewhere if possible...or at least put some rubber spaceres under the mounting holes.