Personally, I wouldn't run stock wire the whole length of the car, but from the kick panel to the speaker in the door is fine. I actually have 200Wrms to each of my front speakers and it sounds fine.
See
here for a speaker wire calculator. I put in 200W, 1ft (30cm) long, 20ga wire (not sure what stock is but it can't be smaller than 20ga), and 4 ohm... It shows i'd have 198W instead of 200W, no one could even hear that
If I change it to 16ga (which is standard aftermarket speaker wire), it shows 199.2W which isn't worth the effort of pulling the grommet apart.