These Asus router models have what you're wanting feature wise:
802.11ac:
RT-AC66U
RT-AC56U
802.11n:
RT-N66U
I don't have any personal experience with Asus routers, just their motherboards. But their motherboards have been good so far, and as mentioned I've heard good things about their routers.
The above models are around $150+ I think. You can drop under $100 if you lose the requirement for a separate guest wifi network (RT-N56U).
The Buffalos are hard to beat price-wise, that's why I bought the one I did, hopefully they've improved things a bit in the past couple years.