Well, yeah, it would. 1200W at about 85% efficiency is 180W wasted as heat under full load. Thats the same amount of heat given off by an overclocked quad core processor. The processor gets a massive heatsink, complete with one or two good fans, or a waterblock. The power supply gets an awkward airflow route, one 120mm fan, and the best they can do with heatsinks within the atx packaging.
Every 1200W, air cooled, atx power supply is going to be loud. The only other option is to let them run so hot that they burn out.
Thats wrong actually my Antec HCP 1200 is pretty much silent, and the noise we was talking about with the ZX 1250w is nothing to do with the fan it's coil whine, they are just a bad design same as the Z series were.