Netgear has this fairly new, small and inexpensive RP614 ... for the price (around $50) it's a steal; you'll get 4-port switch, router and (NAT) firewall, all extremely easy to setup. It has supposedly some packet inspection as well, which I didn't try. I bought this unit for my father-in-law to protect his RR connection, smooth....
I use myself old Netgear RT314 for a couple of years, great box, never any problem.
You absolutely cannot get "true" hardware firewall for cheap, so assume these would be the devices you might wanna consider.