Upgrading my ancient TP link router (54 mbps) it lags so much when someone is using a wifi connection, so I needed to replace it with a cheap but decent router.

Need router that has QoS (bandwidth control) features, good wifi signal (router is in 2nd floor, thick walls, 3 rooms downstairs), and preferably can support multiple devices without slowing down.

My Initial Choices:

Asus
Asus RT N12+

D-LINK
Dlink DIR 605L wifi N300

TP-Link
TPLink WR841N | WR841ND

Leaning on the Asus routers because of feature rich UI, but still need convincing. And it is worth it to invest for dual band routers? (PHP 3k+)