Decent router with small footprint?

[dismas]

My apartment came with a router but I'd prefer to use my own hardware. What's a decent router that can handle at least 400 Mbps wifi that will fit in this compartment? Preferably one that has good custom firmware support. I value stability over performance.

For comparison, the existing router is about 7" long, 2" wide, and 10" tall.

 

[fryedchikin]

Take a look at these. RouterOS is highly configurable but does have a bit of a learning curve if you are new to it.

hAP ac lite
hAP ac lite TC
hAP ac²