Vertical or Horizontal

[TaroSarask]

So, I'm finally buying my 360 tomorrow.

 

Fundamentally (i.e. with regards to RROD, noise etc.), is it better to keep the box Horizontal or Vertical.  I don't have an entertainment center that will allow me to keep it upright, so if I need to do that It'll have to sit on the floor.

 

Thanks in advance.