I've got a 2001 Toyota 4runner. It's got 4" in the rear. I'm going to due a full overhaul including a sub. I've been looking online at Sonic, Crutchfield, Woofers etc, and even some manufacturer websites and they all call for a 6.5 in the rear. I've looked at speaker adapters.com, metra, and scoche, and they only have 5.25" adapters so this is confusing to me. I'd like to have 6.5's back there just not sure it they will fit or what adapter I need to buy to make this happen. I know I will have to trim the inside of the door panel since there is a ring there which is fine. Also, measuring the speaker grate portion of the door panel it too is only for a 4". So I guess I will lose out on fidelity or how it sounds due to this if I go with something larger in size because the speaker will be bigger than the grate?