Replacing the speakers was simple once you have the proper bits in hand. You WILL need THE RIGHT adapters plates since Toyota uses different bolt patterns for every frickin model and year it seems. Dont waste your time on amazon with off brand adapters that say "fits your Toyota 4Runner". Unless its a Metra kit its almost certain to be wrong. Went through ordering 2 of them before giving up and spending a few extra bucks on the Metras. You will also need the plugs to attach to the factory harness (they are cheap). The 3.5" dash speaker required a lot of modification and I would NOT recommend going that route. Just stick to factory size and it too will be a simple install. Once you have the right parts it takes a few minutes per door to install and reassemble.

YOU WILL NEED AN AMP(S)! Cheap paper cone OEM speakers will make sound with very little power but will damage and distort at louder volumes...Stronger aftermarket speakers require more power to move them but are much more capable at higher sound levels. Once you install the kickers (or any aftermarket) you will have to crank the factory headunit almost to max to get an equal level of sound. Once amplified properly however, the Kickers will output much more than the factory and with far better sound quality.

I am planning on getting the TacoTunes.com setup (really impressive kit) since its plug-n-play designed for our vehicles and very compact. Both the 400w 4-channel and the 1000w mono fit on one plate under the passenger seat. I'm too old to have giant flashy amps that are all show. Now I just want them to do the job and take up as little space as possible.

Hope that helps!