I bought these speakers for a 2003 Avalanche.
I replaced the factory with these using a decent 4 ch. kennwood amp. I mounted the tweeters flush with the supplied housings. When I was done I was a little disappointed with the sound. When I raised the volume I got distortion. I was sure I just needed more power. The kennwood was probably putting out about 100watts per ch. (it was given to me & wasn't in great condition)
The peak on the 6501's is 300 so I swapped the amp with a pioneer 760 watt 2 ch. I left the gain all the way down and tried it. The sound was incredibly loud! No distortion and I couldn't stand being in the truck with the volume all the way up! I wanted to close my eyes and cover my ears. I read someone's review saying they can't handle power. It's a lie! They can handle it! If you want the most bang for your buck a head unit by its self won't do it. My stereo does 80 x 4 and didn't do the speakers half the justice they deserve.
Keep in mind the location of your tweeters makes a difference. Drill your holes big enough so they are free enough to swivel. If you have to fight them in your holes too small.