I think it's better where it is (
http://img231.imageshack.us/i/img0822d.jpg/) than on an enclosed shelf as the hot air from exhaust vents at the back is going to get sucked in by the inlet vents around the edge of the PS3. Just move the desk as much to the right as it can (move the bin) and raise it off the carpet by 10cm as you planned. Just keep in mind what it says in the manual.
- Place the system at least 10cm away from a wall surface.
- Do not place on a carpet or rug with long fibres.
- Do not place in a narrow or cramped space.
- Do not cover with cloth.
- Do not allow dust to build up on the vents