Advice: Which Modem to Buy

I need some expert advice to buy a Wireless Modem for my home. My home is a 3 bedroom apartment with over 2000 sq ft. My Airtel Broadband connection is in one corner of the house. I want to know which wireless modem should i invest that will give me good airtel signal and speed at the other end of the house which crosses 3 walls. (i have a 8mbps airtel broadband connection) .

Budget.

Budget is Approx 15K. But actually it is not an issue.

Go for TP-Link Archer D9, costs around Rs. 12500 on Amazon India. This is a modem+router.

Archer C9, if you just want a router.

Cheaper options are there. Since you said the budget isn't a problem, I suggested these models.

Thanks .. Budget is actually not a problem.. But I have been making repeated same investment on wifi modem and router.. But it was never giving me the speed and availability across rooms ...
Hope this recommendation helps

I've a relatively lower end model - TP-Link TD-W8961ND modem+router for my Airtel Broadband. I live in the 3rd floor and I get signal in the car park at the ground floor albeit on the side of the building where my router is kept. I'm happy with it in the last two and a half years. I'm planning to switch to an AC router as I now have three 802.11ac devices.

Also, TP-Link TD-W8968 is a good lower end model; it has EWAN unlike TD-W8961ND.