Wyo11Scab

iTrader: (1)

Not much if any. You won't notice a difference until you go to components that use a real crossover instead of a capacitor.

Pauli18c

Go components and don't look back, you wont regret it.

Cutting the hole for the tweeters is a cake walk. Just buy a hole saw, the trim ring around the tweeter covers up any little imperfections from the drilling and you and mount the crossovers anywhere inside the door panel or inside the cab and just run wires to the speakers.

JorgeRod54

Where would I mount it so that it doesn't interfere with the window

Wyo11Scab

iTrader: (1)

triangle top of door

JorgeRod54

Where the air conditioning duct is at?

Pauli18c

Correct. There's plenty of room once you take the panel off and look. That's where mine are mounted.

PondJumper

Id go 3 way. I had a set of pioneer premier 3 ways for a long time and was very happy with them.

Largen

I would agree with Pauli18c, it's worth it to spend a bit more on a good set of components, it will boost your audio performance alot, and should be something that will leave you happier with your system. It really all comes down to personal preference, but doing it better the first time is usually a better route to go.
Also the difference between multiple or single tweeters is pretty hard to say, in theory it can help, but at the same time it isn't usually needed, a good set of components can cover almost all frequencies a speaker should with one tweeter and one mid woofer, it mainly comes down to quality.
Good luck on your choice! I would choose components myself but it will cost more.