Re: new speakers, do i need a harness?
The only place you should be using a harness is with your head unit, because head units are a BIT*H to hook up without harnesses. Just cut off the clips on your factory wiring and figure out which is pos and negative.
Looks like you have everything you need.
Also 4 way speakers are a gimmick, you only needed 3 ways. And that box your using is probably going to ****. Look into building a better box for your subs, but if you like it, go for it.
Yes that is a 5 1/4th audiobahn mid speaker in my civic's headrest. circa 2006.
2000 Celica GTS
Powerbass 2XL-60.3C 3 way
Dayton Ultimax 15", sealed 4cuft
Memphis 16-MC5.700 5 channel