Whatever you go for, make sure it's an ethernet based solution. Forget about USB from the outset. Ethernet connections are reliable - throw in a USB router and you're asking for trouble.
See here for some info on the dsl-504 (add an access point to it and your printer if it's network ready):
http://www.pprune.org/forums/showthr...threadid=84084
Plenty of other similar stuff out there. No real need for a hardware based firewall - Zonealarm Pro works a treat with wireless networks - install it on all PCs/Laptops. Think about wireless security and ensure that your chosen access point allows you to restrict access by MAC address in addition to WEP security.
Just my thoughts,
Osbo