most efficient audio upgrades? (2010 II, non jbl)

so i just got my prius and i'm generally pleased, but the sound and functionality is pretty mediocre. i don't need volume or bass, just decent quality. can't afford to throw too much money at it so i figured i would ask: what's are the biggest bang for the buck upgrades, or what is the order that people generally follow with these? amp>speakers>head unit (or vice versa)? once i nail down what's most important (or what the weak links are), i can figure out brands and models and such, or what's the easiest/cleverest way to go about it.

my concerns are decent price and quality without taxing the electrical system or having to mod or gut the car, if possible. i can live with the head unit for now but if it has to go i'll be ok with that.

my particular car has bluetooth and a separate mic, but no usb connections (just aux), which is problematic for me. no charging and no control of any kind from the head unit or steering wheel won't do.

ideas and experiences appreciated. thanks in advance

 

that was my first suspicion/fear. i was hoping to scrape by for now just adding the factory usb connection and maybe an amp.

that's been my habit all my driving life, too. just wanted to be a little smarter about it this time.

now that we've settled that, i suppose my next question is: what is worth keeping? does it all need to be replaced (eventually) or will a decent head unit be "enough"? i was looking at the alpines myself, but i like the idea of that fancy chinese one everyone's after, if only to properly fill the void- not a fan of the negative space and bracket look.

 

your photos are both heartening and disheartening at the same time. at least it gives me an idea of what is possible, not that i could pull that off on my own. lot of ideas, though, so thanks for that.

a couple questions: what did you use for sound dampening? and why didn't you just replace the squawkers in the dash? doesn't someone make something that fits?

 

as i'm researching further, it seems that i should focus on the head unit and squawkers for maximum benefit. and possibly an amp to high pass the squawkers and/or low pass the front door speakers. i like the idea of two ways in the dash, but would probably stay passive for ease. doesn't look like they make in drop in replacements, but some gentle carving seems simple enough to make everything fit as stock would.

a four channel amp would handle the dash and door speakers, but would a head unit still drive the two rear speakers acceptably? or could i expect a decent head unit to properly drive all six speakers while sending the right frequencies to each?

so many questions, so much to sift through...