i can buy an older model boston acoustics comp 5-1/4 speakers for 75 bucks or i can buy some new 2 way 6 1/2 polks for round 170 (my jeep has 6 1/2 cutouts in the door. which ones should i buy if i was alot of sq and also pretty lound. should i get the 6s or 5s inch speakers. does the size make a diff in the loudness.