Then get this but u need a separate modem with this but remember wired connectivity will give double the performance than wireless u can use this with u r existing airtel modem Flipkart: Asus RT-N16: Router
Dude check your airtel modem light from verry close if the power light on it dims n blinks(i mean not pure strong and steady). Then you can fix it by two methods because there is a menufacturing defect in airtel modems(in their pwr buttons).
No you didnt get the point that flickering happens when powr is not coming to modem properly and this is why their modem dont function properly. Best solution is open modem and remove the button and solder the power points(but this will make your modem perma. on).
I would go with the Netgear N300 ADSL2+ Router. I'm personally thinking of buying it next week for my home setup. Its 300 Mbps, though not gigabit. The practical speeds of 802.11n is nowhere close to 300 Mbps on 2.4Ghz. Its available on flipkart @ 4232 bucks. And I was getting it for 3800 at SP road in bangalore. Did a bit of research and found out that this is one of the best models in this range after looking at Belkin and DLink models, though it runs bit hot.
I've been using the Airtel modem/wifi-router combo for the past 3 years.
Never found any problems with it. The reason people prefer separate modem and router is, if the modem burns out due to a power surge or something, the router will still be running. But, with Airtel, there never was this problem as all there connections are mostly underground cables. If you want to be on the safer side, you can use the surge protector in the UPS (If its available) for your telephone line.
No idea about other models which you have mentioned.