You may want to have a look at
this. Kofax are a distributor I have used in the past and cover devices from 10's of pages a minute to 100's of pages a minute. You may want to look at the Visoneer and Xerox.
I have been out of it a fair while so not positive what the pricing is like but those and the low end Fujitsu scanners should be pretty good.
To get a feel for pricing I sometimes use
www.tradescanners.com as they let you search by price and basic features. I have never purchased from them so cannot pass comment on their service etc.
Hope this helps
Pev