I have the Brother HL-2140, but it's black-and-white and non-duplexing and thus neither of the two things you requested.
However, there is a slightly higher, similar-looking model that
does duplex. I don't have personal experience with that one, but if it's anything like mine, you may want to look into it.
As others have noted, throwing color into the mix--especially color and duplexing--will make you choices a bit more scarce and higher-priced. If I need color printing, I find that I can do it at my school (50¢/pg, a bit pricey, but their B&W printing is super-cheap and nice in emergencies, and we get $10 credit per semester). Some also buy a separate, usually inkjet, printer for this. I commend you for steering away for inkjets for anything besides low-volume printing (but not so low the cartridges dry up between use
), but if that describes your color printing, it may be worthwhile.
I should also add that my non-duplexing printer isn't the end of the world: on Windows, there is software duplexing that helps you turn the pages around, but you can fake it on OS X by making presents to print the even pages first, flip them (one of two ways depending on whether I want long- or short-edge binding), and then print the odds. But automatic duplexing would definitely be a lot better, even if those machines tend to be a bit larger.
EDIT: Forgot to mention: with many Brothers, there is a trick you can use to get more life out of the toner. Many of their printers detect toner level by shining some sort of light through a hole in the side of the cartridge; if it makes it through, they warn you of low--and eventually no--toner, even when there can still be a decent amount remaining. Covering this hole with black electrical tape (or really anything) after it warns you of low toner will keep it shushed until you actually notice the toner running out yourself. Search the web for your printer to see if it is one of these--the HL-2140 and MFC-8890DW are two that I know are.
