I did some googling and such and it turns out that the PSU has a fan in it, was a surprise to me, I have a TV stand (without tv) which has all our devices on and underneath where you would normally have the vcr/dvd player is where I shoved all the power supplies for the on top devices, cables, wireless router etc etc so it's possible the 360 PSU was getting a bit warm (hence the extra noise) so I blew it out with some compressed air then put it on the floor in the corner of the room as far away from the 360 as possible, definitely seems a bit quieter now, also related is that the delayed shutdown is a cooling down mechanism (a bit like a projector) so if it's a bit hot it won't shut itself down properly until it has cooled a little, guess it's better than having any kind of RROD like the old 360.