yea the Clarke shhhh machines are fairly silent but are also about £1400. My mate has one its a lovely looking piece of kit. but I find my belt drive one is quieter than some of the direct drive units you can buy and cope a lot better with demand.
My main reason for getting the unit I got is if I have a problem with it I can replace either the motor or the pump my self and it has very little down time.
If I had the clarke unit I couldn't go to my local engineering suppliers and buy a motor or pump off the shelf to fix it that day..