By router, do you mean wireless? Because most of the "high"-end stuff is not going to be all-in-one. That is, you'll have a separate access point and router.

I haven't by any means tried everything, but the only access point I've never had any trouble with in an office environment is a Cisco, an 1131.

As far as routers themselves go, I've never had any significant problems (quibbles, yes) with any of the major players: Cisco, HP, Juniper, Foundry (now part of Brocade), Extreme, … I'm sure that there are more I'm missing.

For firewalls, all I can suggest is to stay away from Cisco. Their firewalls are just complete junk.