I have a craftsman 12 gallon, 5hp vac and have been very please with it. I really don't know how much more suction power I could ask for--I inadvertanyly sucked up two MF towels into the vac when cleaning the car (with 2 1/2" hose). I just bought the 1 1/4 inch hose for it to clean the car (littel easier to use for cars) and will see how this works.
I got the vac on sale for $60 this past summer and got the car cleaning attachments included.