It is very easy to make X-Boxes v1.2+ almost totally silent for only £18
A 70mm, 7v, Acoustifan is a perfect replacement, plugs into the standard XBOX fan. It is almost silent at 7v and when combined with the acoustifan rubber gasket it is imperceptible at 10% speed in XBMC and only just audible at 100% speed in games.
If you have a 1.0 or a 1.1 XBOX with a GPU fan then you should sell or ditch it and get a v1.2!
Not quite sure why you'd want that much storage. Only XBOX native games need to be on the XBOX hard drive, everything else can be on the network.
Not to mention that 1.5TB hard drives are still stoopid money at the moment. You can get a 750GB for less than 1/4 the price.