Mikrotik hardware if you're looking for hardware you can upgrade.

I haven't found the need to upgrade my hardware in a couple of years so I don't know what the market currently looks like. I'd just look on the OpenWRT wiki or forum and see what is best supported and buy that.

Also, Atheros radios are generally supported really well on Linux, so I stick with hardware that has an Atheros chipset over something with a Broadcom radio.