I just installed a Pioneer Ts-Wx130da underseat sub, goes pretty good. I unfortunately ruined every stereo I had with a big install about 10 years ago on a past car. The whole stereo is ok, the tweeters seem to lack high end clarity, the speakers themselves sound a little hollow, and the sub does a good job filling in the low end, but doesn’t overlap frequencies well with the speakers. I’m resigned to the fact that the factory stereo just outputs a dogsh*t signal, and because I’m using speaker inputs on the amp and sub, I’m essentially just amping an already sh*t signal. Without going completely nuts and putting in another head unit, amps and sub, I’ve pretty much hit a limit I think.