How much to install an audio system in my car?

My car is a 2001 Honda Civic DX Coupe.

I want to replace the stereo and also get subs and an amp. I may also need a sub box. Also, I'm new to audio systems and subs so I'm not sure if I should get a pair of 10's, 12's or just a single 15. My budget is around $250-$350 if that's possible. What would you guys recommend?

That car is a small car, judging by my own experience I could install radio, amp and subs in 4 hours at most. A shop will charge $70-90 dollars per hour so it's probably about $350. I would highly recommend learning how to install it yourself, it is one of the easiest things I have done.

That's a small car you got. A 15 will not fit inside that car.

I would recommend a 10 or 12 for that car.

The type of box, it could be ported or sealed depending on the sub. Some subs perform better in sealed and some subs perform better in ported.

The type of head unit, there are Kenwood, Pioneer, Apple, JVC, Clarion etc…

To be honest, you will need to spend more than $350 for all of this. Most head units are around $200 - $300. Most monoblock amplifiers are around $150. A good enclosure is $100+. Subs range anywhere from $30 - $500. Not only that, you also need to get the wiring kit for the amplifier. Etc…

Don't go out and buy the cheap stuff because it will perform cheap. In car audio, you get what you pay for.

I have a 97 Civic DX so I assume the cars are similar in electrical and size specs. I'll put down what I have in mine because I've been through a few systems till I matched this setup and the sound is great.

Pioneer head unit - about $180
Pioneer 3-way speakers - $60 a pair on Amazon
DB Drive 500w 2ohm monoblock amp - about $180
2 Kicker 12" 4ohm 250w RMS Comps - $60 each on Amazon
Sealed dual box - I think it was about $100, maybe a little less, can't remember.
6AWG wiring kit - about $30 at Walmart

After going through a few systems, this is the setup that sounds the best. Clear highs and mids and rockin' bass and all volumes and all genres of music. This amp good quality and comes with a bass knob which is very convenient for controlling the amount of bass you have at the tip of your fingers. Pioneer head units come with many options for tuning to provide the perfect sound you want.