Personally I would go with a good quality 6.5" component setup in the front run off an amp along with a sub in the boot. If you must have back speakers run them off the headunit as they are only really there to create a bit of rear fill.

Think of it as going to a concert. You stand facing the stage not with your back to it. so you want the quality sounds coming from in front of you.

Why people put tweeters in the back or mount them in daft places (hi up the A or B pillars) is a mystery to me

All I have in the Escort now is a set of 6.5" JBL's up front run off the headunit as the car is stripped and I'm not too fussed by sounds anymore