Motul is the best, but is it really necessary? probably not, switching all the fluids to synthetic might release a couple extra ponies, if nothing else will be an improvement and lessen the damage during cold starts.
Check your transmission fluid with the dipstick and whipe it on a white paper towel and look for black/brown specs as this indicates wear in the transmission. even if no specs are found if the fluid is not a deep red I would change it, if it has gone pink I believe water contamination. It takes 2-3 drain and fills to really eliminate all the Auto trans fluid as much is stuck in the torque converter, but even changing it once is a good start.
for your rear differential you can use a GL5 fluid, this will reduce drag slightly over what's in there or GL4, for your front diff / Transmission if manual use a GL4 synthetic. if you wan't to really clean your engine run a conventional oil for 2500 miles and then drain it and switch to synthetic, the idea is to drain it before it breaks down fully leaving a clean engine once you put the good stuff in.