What does 'inexpensive' mean to you? I am otherwise-supremely-happy with my commercial pfSense router, if Comcast gets their v6 poop in order I'm sure I would be even more ecstatic with it.
Around the $500 price range for 24 ports, I paid $150 for my TP-Link T1600G-28TS which is a fully managed "L2+" switch with basic Layer 3 routing functionality (but it's IPv4 only).