I'll just add...while not for the security paranoid, our AP's themselves block non-established inbound traffic and perform NAT - which is about 90% of what a SOHO router/firewall does.
So the selection should mainly be based on other features that might be important such as web content filtering, application security, deep packet inspection, VPN etc that more sophisticated firewalls provide (virtually all soho "routers" are actually firewalls by definition - they block by default)
The double-NAT usually introduced by using another product can also make things a bit more complex when you do want to introduce traffic (such as to a home NAS)
FWIW I plug straight into my cable modem - no router/firewall (but I also am all Mac...) And no I won't tell you my IP address 🙂