IMO, while many try to avoid EQ use in their home stereo rigs, it makes much more sense in car audio. There are a bunch of automated EQ units made for cars. Especially with aftermarket car stereo, I would budget for one of these units.
BTW, I just made a huge upgrade in my car stereo sound - by buying new tires!! My car is known as a pretty noisy vehicle (2004 Subaru Outback wagon). I have always loved the 6-disc in-dash changer, and the factory audio is suprisingly detailed and fairly smooth (two sets of mid-woofs and tweeters, plus a "subwoofer" of sorts in the rear deck). But when I needed new tires, I carefully read Tire Rack reviews of possible tires, especially regarding noise. There is quite a difference in the self-noise of various tire types. I ended up with a Goodyear Assurance Comfort Grand Touring model, ~$450 shipped for the four tires. Huge difference! The noise floor has been reduced dramatically. I can hear a lot more detail now, and I have been listening at lower volume settings for the same apparent volume levels as with the old tires. So, that's another thing to try. Just my $0.02.
BTW, I just made a huge upgrade in my car stereo sound - by buying new tires!! My car is known as a pretty noisy vehicle (2004 Subaru Outback wagon). I have always loved the 6-disc in-dash changer, and the factory audio is suprisingly detailed and fairly smooth (two sets of mid-woofs and tweeters, plus a "subwoofer" of sorts in the rear deck). But when I needed new tires, I carefully read Tire Rack reviews of possible tires, especially regarding noise. There is quite a difference in the self-noise of various tire types. I ended up with a Goodyear Assurance Comfort Grand Touring model, ~$450 shipped for the four tires. Huge difference! The noise floor has been reduced dramatically. I can hear a lot more detail now, and I have been listening at lower volume settings for the same apparent volume levels as with the old tires. So, that's another thing to try. Just my $0.02.