I also think the floor is still the best places for the pump. I did put some heavy carpet material under mine and made sure none of the attached hoses were hitting anything making noises when the pump is vibrating.
My pump is right next to the 6-gallon water heater and not real bad on noise when you close the cabinet door. The added carpet material really did help out...
I found this on-line showing what one dude did to make his pump quieter... Food for thought I reckon haha...

This on-line photo may be the surge or accumulator tank TRACKRIG was talking about. Sounds like a good idea as well... This guy says he bought the tank at Home Depot...

Roy Ken