I have a 2002, 2-Door, 4WD Blazer where the OEM speakers are going out. Namely the 2 6.5 inch door speakers.
Looking on Amazon I found for the doors, and for the 2 in the dash and 2 in the rear.

Watt requirements are 150w per 6.5 inch, and 125w per 6x4. I'm still running with the OEM AC Delco audio deck right now.
Will upgrading all 6 speakers be fine in the setup?
If not, what if I just did the 2 door speakers only?


Side Note:
I took my whole dash apart not too long ago to replace the heater core and fix some minor things on the HVAC box. During the process, I took note of the type of OEM speakers that are in my dash, and they seem very lackluster. Replacing those will be a huge boost in audio quality, but I don't want to get into having to rewire everything if I can avoid it.

 

The front speakers went out in my 98 blazer and I just went to AutoZone and got a 2 pack of Kenwood speakers for 45 bucks. After a break in period they have enough power with the factory head unit to make the mirror slide down and shake the doors. They are also rated to 300 watts I believe. As for the dash and the rear door I don't really know what they are, I believe the rear doors should be the same speakers as the front unless yours I'd different than mine.

 

Look for high efficiency speakers dB/watt/meter @ ohms or dB/volt/meter (have to convert one or the other to directly compare) if you're going to power with the factory deck. No way it is 125 watts x 4 - not even a minute chance of it. Big power handling speakers are seldom efficient speakers. AFAIK, the speakers in your dash are tweeters and the frequency is determined by electronics in the wiring near the speakers.