I second the Unifi APs. If you only need an N version, they run around $80-90. The AC models are considerably more.

As the resident Google fanboy, I'd also check out the OnHub made by TP-Link. It has an impressive antenna array that reaches farther than any other home router I've tested so far. I have no idea how it'll do with your concrete floors, but in my own home it's able to go through two floors (wooden joist construction), a stairway, and several walls to a guest room in our basement. We've had people stay there several times and they've had no connectivity issues. When I test the signal strength it's still very good.

Anyway, just a suggestion. It's more expensive than a Unifi AP, but if you have to replace your router anyway, it's probably roughly equivalent.