Okay well I know I don't have a Fit, but I figure audio is pretty universal, at least what is good for what price, soo...... For 350 would it be possible to have a decent set-up with a 10 inch sub, amp, 4 new speakers, and a new deck? single DIN deck 6.5" doors, 6x9 rear deck......i can make a box myself for like 20 bucks....

 

i think it'd be better to just get a deck, sub and mono amp first. You'll be pretty happy with the results im sure, if not you can add the speakers later. Honestly all the people that say having front speakers only is fine... ITS TRUE! i didnt believe it but i think front speakers only is good. Just keep the rears for now in case someone sits back there, but it's not really needed for good sound

 

all of that doesn't seem realistic for 350 bucks. not sure how old of a car you're putting this in, but if it's a newer car, you can get away with very little:

in my fit, i put in a 10'' JL Audio sub with a Cadence 600 watt amp. with a wiring kit, i got a fairly good deal on it for 320 bucks on woofersetc.com.

it's wired up to my stock head unit with a ac/dc converter, and it sounds great.

and jason's right, most people only change out front speakers and leave the rears as just "fillers".

 

Agreed with this. In my experience, rear speakers turned up to high volume just make my head ache. No real need for them. If you have to put them in they're just supposed to be "fill" for the front speakers - so set the fader to the front

Stereo imaging is better noticed if you have just front speakers. Think of the car as a concert venue, and your dashboard is the stage. Your vocalist or lead performer is dead center, with the other instruments fanning out from the center to the sides and back of the stage. You can get this imaging by proper speaker placement and tuning.

With that philosophy, it makes more sense to have just front speaker drivers. If you're in a concert, it doesn't make sense to have sound blaring out BEHIND your head when the stage is right in front of you.