Good morning. Let me first ask what do you mean by “tuning”? An EQ can adjust certain frequencies but if you’re dealing with a stock or upgraded (still stock but slightly better speakers and amps), the only adjustments you can make would be dampening material added to doors and trunks. This would effect audio resonances at certain frequencies. You can also add foam baffle baskets (XTC is one company that comes to mind) to your mids because act like a foam speaker enclosure. I even heard of people adding them to subs that are used in a free air enclosure (using your trunk as a large sub enclosure). Doing a quick search on your car, instead of RCA’s, I see wiring harnesses. Not to sound mean, but you’re extremely limited on your options.
Is this your dream car? Do you plan on keeping it for a large number of years? If your answer is yes, my suggestion is scrap as much as you can (head units usually control air/heat and navigation and you might have to keep it) and replace everything. Go to a reputable car audio store (not Best Buy) and listen to a wide range of mid/tweet separates. Not all speakers are created equal. Ask the installer of the store about sub options. Sub size, enclosure type, single voice coil to dual voice coil. Amps and power requirements and if you want total control, a parametric equalizer. Sound Stream, AudioControl, Stillwater Designs (Kicker) are a few that come to mind. Cars are very imperfect environments for sound. Parametrics give you awesome control over very specific frequencies that need tuning. I remember Hifonics had an in-dash 3 band parametric/2 way crossover unit that gave you great control within arms reach (I think it was the Series VII Ceres).
This is a nasty rabbit hole you can fall down into. I am a recovering car audio addict. The money spent, the time cutting MDF, working out Theile Small specifications, Liquid Nails under your nails, dreaming about the clam shell design for the two Punch 10’s and leaving room to get to your spare tire in a 1986 Honda Civic hatchback. Using Kimber 8TC for your Bowers and Wilkens 5" mids and Madison 1" poly tweeters…I could on for days.
Long story short, you are very limited by what you can do. If this is not a car you will be keeping for years, I would live with what you have. If you love the car and want to take the plunge…do it right. Good luck