Looking for a GOOD commercial vacume? I clean a business center (about 5-6,000 sq. ft of carpeted area)...

I clean a business center (about 5-6,000 sq. ft of carpeted area) and the nouns that is carpeted attracts saline, sand, rocks and paper pieces on the carpet.( alot of use daily and have to be vacummed daily also). We have a Hoover Vac. and isn't powerful enough and doesn't pick up alot. Need some help out in picking out a POWERFUL H.Duty COMMERCIAL Vacume that picks up larger items, small rocks, sand, etc contained by 1- 2 passes just. Can we get some models on what would be recommended... Help needed. MUST be a COMMERCIAL nice and a good one.
Condenser or tumble dryer?
Answers:    The "Simplicity Commercial" element is the best unit I ever used. I have a cleaning business and put more miles on that thing than my sports car!!! It has a metal housed motor and a bypass system, so the dirt doesn't move about through the impeller. It fell down many flights of stairs and didn't miss a defeat. Also, it has GREAT suction. They run roughly $400.
I wish you luck!
http://www.simplicityvac.com/products/co...
How can you remove Sharpie and White Out...?
Several brands come to mind. For uprights, Clarke, Royal, and Kirby. For a canister vac look at Electrolux.