Yes, its a start, but not quite a system.
Be care ful about running factory speakers off your head unit. A lot of factory systems have gone to 2 ohm speakers and that will fry most head units, I don't think the pioneer has overcurrent protection, just thermal shutdown.
12-13 year old stock speakers will probably quit soon anyway.
You really asked for opinions, didn't you? And you are in the SQ section?
Nothing wrong with the pioneer, ultimate or infinitys. But you really need to replace those factory speakers and get another amp.
That pioneer deck has 6 rca outputs and built in crossover. Celica is kinda small for 4 channels, so i'd give up on rear speakers, put all your money into a good set of 2 way component speakers and a 4 channel amp to run them active, making use or the crossovers in that deck.
TS-C160R & TC6004 would work well.
