8 speaker celica head unit upgrade help!!! Options

[chris32880]

Hey guys I upgraded my speakers with pioneers, 1 inch tweeters are still stock, the 4 inch top speaker on door are pioneers, 6.5 in back are pioneers. I just ordered 8 inch 400 or 450 watt 8 inch speakers, the speakers weren't a problem at all, now I want to do a double din pioneer head unit, I need to know if I have to buy the plastic for it to go in like a single head unit needs... The celica 8 speaker runs on 2 amps, I found the metra adaptor for the amps to be used te double din head unit I will be using has 2 RCA plugs the adaptor has 4 I need all 8 speakers to work so I need install help I found a forum with info but want to wire everything perfectly and need to know if the head unit I'm buying has 2 and the adaptor has four if it will work or not thanks any feedback will help

[chris32880]

The headunit im buying has 2 rca outputs, meaning a set of 2 of 2 so 4 rca total but I bought the wire harness metra 70-8112 so it has 4 of them im not sure if the rca on those go into the headunit or if the go into stock amp? never taken my celica apart to see it until I get the parts in mail, anyways there is another head unit im thinking of buying that has 2 sets of 3 and 2 sets of 2 but its 150 more... I really want the double din pioneer fh-x700bt or the pioneer 1400 dvd one