Yes, someone is trying to screw you over. What they want to do is increase the sale and then get you to do an expensive install that will include running new speaker wire through the car.
If the connectors don't plug into your stereo just cut them and figure out which is + and which is -
What year is your car?
Also, I really don't know much about electrical circuits but I thinkyou can plug all four front speakers into the two front channels if you want to. Either wire them in series or parallel.
Series for front right speakers:
Deck front right+ -> Speaker 1+ -> Speaker 1- -> Speaker 2+ -> Speaker 2- -> Deck front right-
Parallel
Code:
|---- Speaker 2 ---|
Deck front right+ ---| |------Deck front right-
|----Speaker 1 ----|
I think I'd go with doing them in series because its easier. That's how I set up my subs when I had them and I didn't short anything out.
To wire them in parallel (which I've never done before), I think you would just crimp/solder two separate wires onto the positive wire from the deck, run those wires to the positive side of each speaker and then crimp/solder the
negative wires from the speaker to the negative wire coming off the deck.
I could be totally wrong about this though so ask someone who knows first. I am certain, however, that you can run all 8 off of the 4 channel deck.
8 speakers are great but if you want real bass you need subs. The speakers in the front and rear will cover the mids and highs well enough but still won't put out a powerfull bass.