The speeds some of the OpenWRT gurus speak of overwhelm me. I don't understand how anyone has this type of network available in a home environment or what use you might find for such terrific speed. So living in a world where 20M is something that would be considered a futuristic expectation, my go-to box is the GLinet GL-AR150 (16/64M) selling at around $22US, which does everything I need. I keep one on top of the TV stand in Mexico for VPN service to US-only TV streaming accessories and any other device that needs a US IP, I keep another up on a pole connected to the back of my camper running Rooter (OpenWRT cell modem supported derivative from ofmodemsandmen.com) for pulling in cell signals and since that service is metered, even though 4G is becoming more available across the places I travel, I actually favor 3G to keep me from going over my data limit each month. In my suitcase I have another one with the USB connected to an Alpha device with Atheros AR9271 which is attached to a tube yagi and while backpacking and staying cheap hotels the Alpha and yagi pull in the distant wifi from the hotel office and the AR150 re-broadcasts in the room.
The GL-AR150 device is half the size of a pack of smokes and remains one of my all time favorite portable routers.
(Note I've just starting playing with the GL-AR300M 128/128M but at around $40US I'm not that interested especially with the lower ISP speeds I deal in and also since fast metered cell is more a nightmare for me than a bonus with today's severely limited data plans.)
Otherwise the most powerful router that I've dealt with to date is the Alpha Tube 2H (8/32M) (or try for new 2HP model with 16/64M) which I have feeding the short LMR-400 feeding a 24db parabolic for distant wifi reception. It sets you back around $80, unfortunately but well worth it. I have never tried it at the break-neck speeds some people boast about here, however.
Of course the most amazing router I've every played with that doesn't do much is the one which is the size of a USB memory stick and is priced around $7 US and that is the A5-V11 (4/16M) which does your basic OpenWRT stuff but in the smallest of small packages. (Note that ofmodemsandmen.com provides a Luci version with USB cell modem support for this and other 4/16M USB capible devices.)