[Thomasluke7899]

Well....you can do 1 or 2 of the needed steps with 500 bucks.
You can
Get a head unit and the appropriate dash kit and wiring hardware.
Get a small sub set up added to the oem system.
Swap out the speakers.
If I were you I would start with the funnest part. The bass.
You get the most bang for your buck there.
Unless you like carplay or android auto. Then the head unit makes sense.
It also makes sense if you're not concerned about the bass as much.
But honestly 500 is enough to get a decent head unit but that's it.

 

[Thomasluke7899]

I take it back. Get this.

Sold : Alpine PXE-08505 Dsp

Alpine PXE-08505 Advanced Wireless Digital Sound Processor Using it in my truck now. Works great. Looking to upgrade and get something else. Have box and all cables. I have every single thing that came with it. Item is 9/10

www.diymobileaudio.com

It has enough power for the factory speakers.
You could make it sound great. Then upgrade one piece at a time as you go.
But this is the backbone to any good sounding car these days.
Not just this alpine. But any processor really.

 

[Thomasluke7899]

What's an Aoto 6? Head unit?

If my entire rig got stolen, and I had a hard $500 limit, I'd be looking at the classifieds here, along with Craig,s list and similar. But with a hard $500 Amazon gift card budget to work with, I'd go with one of the Power Acoustics integrated DSP/amp combos. Probably the 5 channel. A bit clunky, way overrated power rating, but sufficient output. $215 on Amazon, leaves enough $ for some decent tweeters & midwoofers, some deadener, possibly squeeze in a sub driver, as well. Having gotten used to fully active + DSP, I can never go back - so I'd be looking for the cheapest way to retain that. It may be that there are more effective ways to quality sound for that budget, though.

Thread about the 4 channel version of DSP amp

I forgot about the Amazon thing. I know a couple that run the power acoustic dsp and they say it works.
I heard one about a week ago but the install was horrible and there was noise. But it was an active set with no protection on some nice old f1 alpine tweeters and they have been for a while now with no problem. So if they can do it you probably do it.
I think I'm about to grab one to try out.