Changing just two speakers?
 

I have a 2002 blazer LS with the cheaper sound system (Delco I think). I want to upgrade the sound system, but i dont want to spend a whole bunch. I found a headunit that came with two component speakers for under $150. If I change the stereo with a headunit and change the two component speakers in the front, then will it make my sound system better, or will the new speakers not sound good in conjunction with the old ones? This is assuming the new speakers sound better than the old ones.

Where did you find this head unit with component speakers for 150? Are you sure they are not coaxial speakers?

at 11 years old, your OEM speakers are not long for this world. You start pushing them, and they'll fart out in no time.

Yes you can change only 2 speakers. When I bought my Blazer, it had Pioneer rear speakers and stock everything. Then I changed the head unit and door speakers, but the dash ones are still factory to this day.

Alton has said, and I have found true, rear speakers are of little use. Down the road you might use the rear channels to send signal to a woofer crossover I dont think that LS blazers have dash drivers but mine has factory wiring for a speaker. If you have true componants you will replace the bass blocker. Sometimes its just easier to run new wire to xo, tweet and mid.