my stereo from 12 years ago in my old mazda sounded way better, yes it was aftermarket, but at the time it only costed around ~$800
JVC HU with USB,
Clarion Power system speakers and subs,
5.25" components in the front, 6.5" coaxials in the back,
TWO 10" DVC Subs sealed box, bass shaker in each of the front seats,
380W RMS amp for the front and rear speakers,
400W RMS amp for the subs,
200W RMS for the bass shakers,
tuned to be perfectly flat for sound reproduction'
this stereo is considered "budget" you can go much higher in price and quality (3 way components front and rear, everything with their own cross overs and custom enclosures, etc)
as far as rankings go
1) high quality aftermarket
2) budget aftermarket (but tuned right)
3) the mark levinson system in the SC430 (wow i was impressed being a factory installed stereo)
4) lexicon system found in hyundai and rolls royce vehicles
5) ...
6) ...
7) Infinity system from my old Genesis coupe (2010 model, not the crappy 2013 downgrade)
8) the system found in the Tesla
8) Bose systems found in corvettes&some GM cars/nissans/mazdas (these sound horrible)
so as far as $2600 goes, you could get probably med-high quality aftermarket and it will blow away anything factory installed. i would not recommend the stock system from Tesla either standard or upgraded. Of course not everyone agree's with me but try listening to an aftermarket system that costs $1000 and is tuned properly, then listen to the tesla's, you will hear what im talking about.