The noise generated by the 735 is primarily from the motor, its the nature of that motor. A helical head will reduce the machine noise to some degree, but a 735 will always be loud.
Large planers will be quieter due to a number of factors, and a helical head will definitely lessen noise. It is also a far superior cutting system compared to traditional straight cutter heads. Putting a helical head on a PM209 will more than pay for itself in the long run.
The tools don't make the craftsman......a true statement often overused by individuals who haven't a clue about quality tools or true craftsmanship.