Router Advice

Hi all I need some help choosing a router.
I am currently with Origin on a FTTC contract and they supply an Asus N16 as standard.
My problem is I am 2km from cab and I have mixed ali/copper "last mile"
My connection speeds are 3mbps down 1mbps up.
The above router loses connection regularly 2/3 times a day on average. This causes a decreasing resync to an already small number.
Open reach have been out several times and the last guy to come out was a diamond. He checked and tested everything from duct to master socket to make sure line was as good as it could be (it is).
He concluded it was a router issue which I concur with as I am now running a Sagecom 2704N and Open Reach modem with no drop outs.
Problem I have is the house has thick walls and this router lacks punch.
So what I am looking for is a router that has good stability and can generate a reasonable wi-fi signal.
Any suggestions will be appreciated.

Forgot to add I have already tried 2 of the N16's with exact same results.

Go for a Netgear R7800 which is arguably the best standalone router around. If that's out of your price range then the Netgear R6400 is an excellent cheaper alternative. Other top class routers are the Asus RT-AC68U, the Asus RT-AC87U & Linksys EA8500 but they're all around the £150 mark, in which case you will be better off going with the Netgear R7800, at around £160.

https://www.amazon.co.uk/NETGEAR-R7800-100UKS-Nighth...

https://www.amazon.co.uk/NETGEAR-R6400-100UKS-802-11...

Nice one that has narrowed down the field tremendously.

Keep the modem and router you are happy with and then add some wireless access points at appropriate locations.

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Most Asus routers if they have an Ethernet WAN port option can be set to access point mode, so no new hardware needed at all to make sure of the Asus, or alternatively you can set up the Asus as an access point following a guide like http://www.coolwebhome.co.uk/wap/configuring-wap.html