Hey... I m using ASUS rt-g32 wireless router which costed me rs 1350 with 3 yrs warranty. m using it with tataindicom broadband and its working with charm. i think these are manufactured for working with every connection like tata,airtel,bsnl etc....
I will suggest you to take it on monthly rental from Airtel itself, because:
1. They will provide you lifetime guaranty.
2. Onsite service
3. Quick suppprt as Airtel have good support.