The Laguna 4200 pump can handle 4200 gph using only 170 watts, thats very efficient.
The cleaning comes from the volume of air rising lifting the media to dislodge the debris. You only need enough pressure to reach the bottom of the filter, then the rising air does the rest. Key is having a huge volume of air rising. I have read of one person using a commercial 60gal air compressor, problem was it put out high pressure and not enough volume. It worked OK though. 1hp spa blowers are ideal, but 6hp and up shop vacs do fine. There is a good article here http://www.koinations.com/cool idea... Vacuum cleaner? really? How would that work better than an air compressor?