Bhai, Toyota sends trash speakers both front and rear. You will be driving the car sitting in the front seat, so you surely need to change the front door speakers. My suggestion would be Pioneer 1720 for front speakers.
Your Panasonic pre is not 50WX4 .. What matters is the rms rating which is 18W per channels ... If you intend to stick by the stock Panasonic pre, then you might go with low power speakers.
Whenever you look at audio equipment, always pay attention to the RMS power and not the peak power.
Since you have already bought Sony speakers for the rear, then no harm if they stay.
