Car Stereos: subwoofer, alpine cda, amplifier

Question
"i have this car(lancer) audio set up at the moment (head unit alpine cda-117 ,speakers  jbl gto 938 & jbl gto 608c and jbl gto 1004 for my amplifier) id like to add subwoofer and amp on it. (preferably jbl too)what can you recommend and what else do you think should i add on my setup.
thank you very much sir."

Answer
JBL subs and subamp should be just fine.  They are not top of the line, and they are not junk.  Pretty good subs and amps for the money.  After that addition, I am sure you will be super pleased with your system.  There are many other upgrades that you could add, but aren't really necessary in a good sounding system.  Hope this helps, Scott