i have apline type r 5x7 coaxials in back, and 5 1/4" round and 1" tweeter in front they built a custom bracket to fit them in but i originally wanted to mount the tweeter on the door or A pillar but this way install was free so i didnt argue.
the 5 1/4" rounds did sound better than the 5x7 on the wall in the show room and the salesman said they will sound better in my truck up front than an oval shaped speaker.
Too bad he was wrong, my rear speakers sound better than my front ones and can handle higher volume before distortion when compared to the front. Yes i know i could make them all sound better by adding a 4 channel amp, but i dont really want to spend $800 CDN on an amp right now. Before i got my sub (10" boston G2, and boston GT 20 amp) i had gone into the shop looking to amplify my speakers not add a sub, but it was the same money for either option and both made the speakers sound better. and i decided if i want to i can then add more power to them down the road.