Hey I'm looking at getting a new pair of front and rear speakers on my Fiesta. It's a P-reg (mk III i think.. lol) If I put some 6*9s in the back and some new front speakers, will i need to make any major changes... any additional insulation to prevent possible resonance etc.? I'm not sure how much to spend either, car speakers seem cheap enough so i guess I'm looking at pretty high-end? Btw, got a sony head unit, not sure which model, its about a year old 4*50w. Sorry, I'm not very up on car audio!