Need a new adsl router

I need a new adsl wifi router for my mtnl connection as my dlink 2750u has died (after 3 replacements).As for budget 2k~4k max.

Now as for my requirements :

1.) Good range coverage for 900 sq ft area
2.) No dlink recommendations pls.
3.) Firmware updates should be easily available.
4.) need usb storage / printer support
5.) class ac and 2.4/5 ghz support
6.) Good A.S.S (after sales service )