Last year I got a WatchGuard XTM8 (810) 10port/1Gbe port firewall/VPN appliance for £50 off eBay (normally £12,000) but with no PSU and no g'tee it worked.
Replacement PSU £40.
pfSense (free) installed with help from some of the forum members as it is a bit finicky having no COM1 but has COM2 on board.
Works like a dream, Intel Quad Core CPU and 2GB ram as standard.
I've still yet to figure out why I need the ability for 500k connections to my home broadband, but at least I'm covered ;)