Perhaps you can buy a mikrotik.com router? I've heard great things about them and they're quite cheap. I was considering buying one to replace my TP-Link router as it finally broke so much I had to do a factory reset and lost my beta IPv6-actually-works firmware.
We've already got a PS50 value (got it discounted dw) netgear extender. I think it's more down to a very old house having very very thick walls. The carrier signal is annoying though, have to disable wifi so that my phone connects to a working 4G rather than attempting a dud signal for 200metres radius.