I recommend 849NU, Schedule your downloads for night and limit your day surfing by avoiding videos and high resolution flash sites. In 849NU with Call rentals + modem rentals your bill might be around Rs 1200, provided you don't exceed your day time usage. I'm using 849NU, my monthly average download happens to be around 40 to 50 Gb (torrents & link-removed). If opted for 512 unlimited, your final bill amt may come around rs 1600 including service charges and all applicable rentals. Finally choice is yours.