While searching around the web I found a thing or two talking about a bass stopper. Basically you wire it into your speaker wires for like you front and rear speakers and it takes all the bass out. They said they are good if you have subs. Does anyone have any knowledge in these. I have a feeling they are bullshit anyway.

It's just a capacitor, when you put it in series with the speaker it makes a simple 1st order highpass filter, which cuts out the bass as advertised. If you have an aftermarket headunit or an amp powering your speakers then you can just turn on their built in highpass filter instead, which will be much more effective than those "bass blockers."

Thanks