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]

So if I don't run subs will it power all speakers? The adaptor from metra for the 8 speaker celica has 4 RCA, so basically how many RCA should I need for the oem 8 speaker to run with the oem amps? And so if I want to run subs ill need more? Just trying to find out info so I can run it or is there a RCA splitter where you can run 2 off of 1 RCA input? I just need some help because I want a new head unit and thanks bro

Still have stock head unit but keeping all my oem parts just for future purposes... I'm not selling parts sorry man