I recently upgraded the "stereo" found in my old 97 Accord. I pulled the stock deck, removed all of the stock speakers (Front and Rear).
I went with a 2 way Zapco component set. 6.5, built a trim ring so the woofer would fit in the stock door location, hid the Xover in the door panel, and mounted the tweeter on the inside of the mirror cover. Relatively stock look. Cast basket, deep basket, great quality sound. eBay.
Deck was an older Pioneer 5500 I think. Craiglist locally.
I bought old PPI and Orion (as in late 90's) amps off eBay. Cost less than $60 each.
For the sub, I already had on hand some older Max Fidelity 10's, so I built a clamshell isobaric box. Ported, with the port built to fire through the "ski pass thru" in the rear seat.
Will carpet in stock trunk carpet, for a relatively stealth install.
Cheap and cheerful, if you are near TO, let me know, we can have a sound off!