If you haven't made the purchase already, check out the HP Laserjet M1536Dnf - printer, scanner, fax, copier in one. It has both a flatbed scanner and a paper feed one(which is very fast).
Duplex printing is present. Have used in office for nearly last 2 years
Uses toner cartridge HP 88A (or compatible).
The manufacturer's page is HP LaserJet Pro M1536dnf Multifunction Printer (CE538A) specifications - HP Products for Home and Home Office products
P.S. I don't work for HP
Available at 24087/- from flipkart, 22500/- from infibeam. Other options are also available from HP, Dell, Canon, Brother etc. Take a good look around FK, Infibeam, snapdeal and also your local market.