2 way or 3 way

What should I go with 2 way or 3 way speakers for my front doors. If i can fit a kappa 6.5 in my door i will go with that but i need to know if anyone has done this so I know it works. If i can't fit a 6.5 i would go with a 5.25 kappa.

2000 Pontiac Grand Am 2 door.

Two ways are good.  You might notice a difference between two way and three way for a front speaker.  I'd go w/ a two way and add a tweeter in the window sail (if you have one).  That's my set up right now (5.25 reference two way and a tweeter in the sail) and my highs are singing (not harsh but definately clear).  Do you know the size of speaker up front already?  I think it's 5.25 but not sure.  If it's that then you could modify the opening to accept the 6.5 (like raydawg  said given the magnet has the clearance). 

Last time I checked, coaxial = Yugo and components = Rolls Royce

I hope I was'nt under a rock that long, although I've seen CDT and other high end building convertible type driver's.

The coaxial speakers i've got are some sweet speakers.  I've got an extra tweeter running to them up in my window sail.  They have some incredible highs with good lower frequency sound.  The components might be better though.  I wouldn't mind going with them but they run normally $100 more than their normal coaxial speakers.