for the aux output to be built in the car need at least to be 2007 or up. Most stocked speakers is like 20 to 25 watts RMS, I mean I don't really stocked radios, I would get some subs first all that, then change it speaker if you wanted. JL audio, JBL, Alpine, infinity, any of those will do good on your car, also get one 12 inch subwoofer, MTX TS8500, MTX T7000, alpine type X, kicker L7, JL w6, any of those will be loud in your celica.