I bought these for my 2003 Isuzu Ascender because my factory front door speakers were going bad on me, one day I was hearing my left speaker and the other day I was not. So I did a little research and decided to buy a pair of Kicker 40CSS674 6-3/4" component speakers from Crutchfield. Once I installed them, man it made a big difference. Deeper bass and crispier sound tweeters, don't get me wrong mines sounded pretty decent when they were new, but after installing these. The sound quality outranked my factory speakers by far. I had installed a DIN JVC KW-NSX1 DVD Receiver from Crutchfield at an excellent price back in May 2013 which is still working like new and like I previously mentioned above, once I installed the kickers component speakers the sound quality improved drastically. I would recommend them to your Trailblazer, Envoy or Isuzu Ascender. My next step would be to install an amp with an sub-woofer for a richer bass.
Pros: These Kickers 40CSS674 6-3/4" component speakers improved the sound quality of my SUV. These are an excelente up-grades at a pretty decent price, yes you may pay a little more, but the quality however on these are excellent and they are very well built.
Cons: You will need to make a mild modification on your factory speaker brackets to fit these in, this modification does not affect the bracket's structural integrity.
For me it was a breeze, but again I like to do a lot of things on my own, that's how I am a handy guy. I took about 90 minutes to do the modifications and installing them into my SUV. You may need to have a little basic knowledge on using a router tool, but if you have friend who does better. You will enjoy the sound of these speaker