hey theo, although you'll probably be creating yer own system from scratch........i bought a turnkey cadillac system from Vertex running two diffusers (prob. overkill) each taking ~150 ft of airline.
1) no problems thus far w/ overheating
2) with the box lid closed, the noise becomes neglible (in relation to a quiet country evening) at around 2-300 ft from unit.
3) the compressor unit and box is less than 2 ft per side but I secured onto a typcial wood pallet to keep off ground and it sits outside next to/above pond.
my only issue thus far is to make sure you build yer system with independantly controlled manifold so you can run multiple diffusers at different depths w/out one hogging air over the other.
