Ok I swapped out my head unit and the door speakers. The old door speakers were 4ohms up front and 9.8ohms in the back. The dash tweeters are also 4ohms and share the front channel with the front door speakers. The head unit says it will drive 4-8ohm speakers, and its max wattage of 54 x 4 is at 4ohms. From what ive seen online if I am to put speakers back in the dash that are also 4 ohms the ohms the fronts with the dash speakers will be 2ohms, since they are connected in parallel. Wouldnt this draw too much wattage from the head units amps if they are 2 ohms when combined?

 

If you have the tweeters properly filtered with a crossover, I wouldn't even begin to worry about it... Well for aftermarket decks anyways. I couldn't be sure about OEM decks, because I think they're crap to begin with lol...

I had my doors/tweets hooked up to the deck before I hooked up my amp. Worked fine aside from being underpowered, but that's a different issue than impedance.

I would say do it, and don't worry about it. Tweeters do not draw alot of power, so you won't have any issues, and aftermarket decks can handle a 2 ohm stereo setup. At least up to a certain extent. Don't be hooking up subs to your deck! LOL!!