Question for people who have had their doors apart

So I am planning on adding a small subwoofer to add some Bass to the system nothing serious - I already killed my ears when I was a kid with 2000 watts in an S10. I used to do car audio competitions and had thousands of dollars invested in my systems now in my older age ( 29 - lol ) I have no desire to do these things. I would like to keep the factory head unit, and am actually very pleased with the Factory speakers minus the lack of some clean low frequencies. I plan on doing a small sub and will install bass blockers on the door speakers, but one question is do the factory tweeters already have a frequency filter installed? I would assume they should since lower frequencies can damage the tweets, but I want to know before I order the parts. Also for those of you using the factory head unit and adding an amp - did you find a convenient wire to tap into for the remote turn on? Thanks in advance for any help you can provide - as always i will post crappy pics of my install once its complete.

 

Perfect Thanks! Thats exactly the information I was looking for.