Silver Efex is indeed very good, one other alternative on the same level as Nik's offering is Alien Skin Exposure 4, which also costs $200, but simulates color films as well, so it's kind of a 2-in-1. You might want to try their demo out too, I personally love some of the punch their color filters can add to your image, even if you don't add stuff like grain.
A big advantage of plugs like these is that you can manipulate a variety of effects simultaneously and see how they interact right away. I'm sure it can be done in PS, but it would require a number of non-related steps and you don't get a preview till you're done, so you needs good idea of what you're doing.