Best bang for buck purchase / install order?
 

Thanks!

Also

Plenty of room behind the seats.....

This is not a plug for Crutchfield, but I was on their site recently to price speakers for my 2020 STX. If you plug in your vehicle make/model/year, they can show you what fits.

But there's one extra little thing they do that might help in your case. They often post installation notes on the vehicle type from one of their techs. These notes will give you some general information about anything you can install, and in the ones I read yesterday, they specifically mentioned amps and subs installed under and behind the rear seats. It's just a general set of suggestions, but they might help you decide what to do.

I like to do speakers and sound deadening first, seem the key to great sound.
I did plan the entire system for my needs and budget, bought and installed speakers, then amp/processor, last item was subwoofer.
That was my way of tackling the jobs, on more than one installation. KM

Thanks

Have done several vehicles in the 50 years of my driving. So no specific source, but if you need help this is the beast source I have found. It may take time but lots of members with advanced knowledge willing to share. I will suggest HushCar Audio (one of the helps mentioned here) for any harness and parts needed. Haven't bought anything from him yet but would have if I had found this forum sooner! KM

I used Noico on my doors, silicone speaker baffles, Morel components in front, integras in rear. may want to start there. Do front doors first with proper "deadening'...plenty on here and youtube. LOTS of options for you, but fronts need to be components. Put tweeters in stock location for now, crossovers will fit at a-pillar or behind HU. you will need to run tweeter wires.

I'd be happy to help out and to make this as painless as possible both financially and with the install. Send me a PM if interested.

agree with others, noise reduction (be sure to read up on how to do this the right way before making any purchase so you don't waste money) is always my first step followed by the headunit (and processor if going that route). those are the beginning and end of the sound journey, if you will, and will yield the most dramatic results on a step by step basis. this assumes the vehicle i am working on does not require the factory headunit for something like heated seat control or similar. speakers are next with the sub(s) happening first. then i head over to www.knukonceptz.com for all new wiring.