Wireless router with a really good range?

Hello. I’m trying to set up my parents house with wireless internet. They got a Netgear router with a claimed range of 35m but the signal was nowhere near strong enough. They swapped it for a Netgear Rangemax with a claimed range of 300m but it was hardly any better. My laptop couldn’t pick up any signal two rooms away – through three walls but with the doors open.
The position of the router is less than ideal, but can’t be changed: it in one corner of the house. The house itself is quite large and has thick walls. Even so, I’m surprised at how poorly the routers have performed.
Can anyone recommend a router that might do the job? Is the problem I’ve had typical of Netgear or any router struggle?

Thanks.