Well, I am speaking from my last car only having 5 1/4's all around and it sucked. Talk about no bass. Could not even listening to my favorite jazz it was soo bad. I don't know if you plan on putting in subs or anything else. but the 6 1/2 will only take you down in freq. I guess 5X7 will not give you much more in size but I can just picture a car with all mid -> high. I am by no means a speaker expert thought so come one other people, reply too.