Audio Systems: Subwoofer problems, fuse box, loose connections

Question
I have purchased a fli trap 12" subwoofer with a 200W amp built in.  I purchased all the wiring speratley and set about wiring this up.  I connected the power to the battery via the 20A fuse supplied with the wiring(The sub also has a 20Afuse connected on the back of it), I then connected the Audio R/L leads from the head unit to the sub. I also connected the ground via a screw to the metal in the floor of the boot.  The problem I had is that the subwoofer required a remote to be connected so that this could be switched on and off.  My stereo does not have any remote output.  I was told that all the remote connection on the back of the sub was a 12V connection and when 12v is applied the sub would turn on.  I took a wire from the 12v input into the car stereo and connected this to a switch then to the sub.  All was working fine for a coule of days then my car just stalled as i was driving and all the electrics went and then the battery was flat.  I took it all out and started again and once all connected again with a new battery my car wouldnt start - It works fine when this sub is not connected obviously something is shorting out somewhere but i just dont know where.    I feel it is a problem with the remote connection and taking this 12v from where the head unit gets its 12v? hope this makes sense - i would like to get it all fitted but i dont want anything happening when i am driving again (luckily the car stalled in a quiet area last time!!)any help would be greatly appreciated?   Thank you...

Answer
Hi Martin!
It's very strange that an amp would kill your electric system, especially the remote since it takes only a small current, connect the remote to the ignition (or Acc) wire going to the radio not the constant in wich case the amp would run always. Also check for loose connections on the battery/Fuse box.