I spent some time over the weekend playing with Pfsense, and I can’t say much about it other than it does what it says. I didn’t throw a ton of hardware at it–the best motherboard I have laying around is a late P4-era Celeron board, and the best network card I could find was, believe it or not, an ancient Netgear 10/100 card with the late, lamented DEC Tulip chipset on it. Great card for its time, but, yeah, nice 100-megabit throughput, hipster.
If you actually configure your routers rather than just plugging them in, you can do this. Plug in a couple of network cards, plug in a hard drive that you don’t mind getting overwritten, download Pfsense, write the image file to a USB stick, boot off the USB stick, and follow the prompts. Then, to add wireless, plug in a well-supported card like a TP-Link and follow the howto.