Get components!!!!!!!!!
Why are you looking ata co-ax at all?
You get a better woofer and better tweeter almost across the board. Yes external crossovers are superior to coax crossovers 99 percent of the time, your still gonna use your amps High pass crossover to keep the 100-80 Hz bass and below away from your components.
SPend the $$ from your external crossover and your coax and get a $100-200 set of componets and get some sound deadning for your doors if you have any extra $
I dont even have the car for these yet and i dont want to get compnents cuz i dont want to cut up places for the tweets cuz when i do eventually sell the car, the system will come out.