I thought I could drop them in. I soldered the connector off the old rear speakers and soldered them onto the new speakers. I plugged them in, and everything but the new speakers works.
I used the same process when I installed new front 5.25" speakers.
The new and old speakers have the same ohms rating.
I'm thinking I just need to get a cheap 37W RMS two-channel amp to run my 90W RMS rear 6x9"
I don't know **** about car audio, so I've been learning all of this as I go.
Also I have the 8 speaker configurations:
2 front door 5.25" delco 4ohm speakers
2 front door tweeters (unknown)
2 rear 6x9 delco 4ohm speakers
2 rear, uh, they look like tweeters, but they can also put out a lot of bass.