Davidefc, for what it's worth I just setup a 120 a couple of months ago. Right now it has 2 XP3's running on it. It has great circulation and the fish waste that is too heavy to get sucked up into the filter intakes rests underneath them, making clean up easier.
Secondly they are both pretty quiet. You can tell that they are on, but no more loud than say a cooling fan on a laptop or computer. Right now I have 4 JDs at 3", 2 GTs at 5", a few Giant Danios, 2 6" Hujetas, a Gold Nugget, a Senegal, and a Delhezi. I will be taking the male JDs out as they mature(breeding project), and plan on throwing an AC110 in a couple of months.
Overall I rate the 2 XP3's as very adequate for a 120 without being overstocked.