Vacuum Cleaners Discussions

I own my own cleaning business and I clean approximately 2 houses a day. I have had a base Kenmore canister vacuum.........loved it, but it seemed to sometimes have a hard time picking up the stones too. I currently use an electrolux ultra silencer.......the only thing this vacuum has on the kenmore $200 model is the convenience of all the extra features, easy release of the beater bar,and on off buttons on the handle, oh and it's super quiet!!!!  I don't like the fact that electrolux has its own tools and nothing else fits. The hair out of my toolbrush came out and the new vacuums have very small bags so I am changing my bag every 3 houses. It sucks pretty good when the bag is first changed but after the first 2 houses it starts to get harder and harder to pick things up. I would not buy this model again. I would rather the kenmore. That all being said, I clean an office that has tons of little pebbles and sand and dirt on the tile floors. The electrolux just doesn't do it. Any suggestions on a heavy duty canister vacuum? I can't spend lots as I just purchased the electrolux 6 months ago and it was $475 (not worth it!) My floor types vary from carpet , hardwood , ceramic tile floors, to linolium so something that would have a beater bar to also use would be great.
Remember I am cleaning everyday twice a day and do a lot of lugging the vacuum around.
Thank You for your help, I just don't know what to do.