Audio Systems: stay factory HU? Go after market HU or AMP?, premium sound system, decent amp

Question
Tom, I just bought a '05 Focus SES with a factory installed premium sound system. The system has a six cd in-dash player with mp3 play back.  I don't have the upgraded Audiophile system.  I am a complete nephyte so bear with me.  My dilema is as follows...I wasn't too happy with the sound of the factory speakers so I replaced them with 4 Alpine 5"x7"/6"x8" speakers (sps-570A)200 watts peak.  The highs and mids are great but the bass on percussion sounds as if my 3 year old were beating on a bucket with a wooden spoon (I had the speakers installed at Best Buy)  Is a high powered after market HU something I should consider or is the installation of a decent AMP an option I should look into, seeing how I would hate to get rid of the in-dash cd changer.  I know I could ask the guys at Best Buy the same thing but I have a feeling they would try selling me both the HU and the AMP.  I couldn't find any info on the factory HU in the Focus and the guys at the Ford dealership weren't too helpful.  I couldn't tell you the output of the factory HU.
          Thanks for your time,
                   Rick  

Answer
Rick,
For great sounding bass you may want to connect a high level (speaker) to low level(RCA) adapter across the rear speaker wires and then connect the output of the adapter to a bass amp. With your premium sound system you have a factory installed amp some where in the vehicle to drive the existing speakers.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net