You can mate as you will be driving its not gonna make a differance if the speakers are going in the back, especially the tweeters! You will need to fit the crossover though as you dont want your mid/bass driver picking up anything over 120hz which it will do if it has not got its crossover on it. The standard tweeter has whats called a capacitor on it, works the same as a crossover but cant take as much current, ie volume. The standard tweeter will be ok if your running your comp's off your head unit and not an amp. Dont worry if you have a high powered head unit, even a 4X50w will only be giving 18-21watts RMS.