The nvidia-current driver is the most recent driver for newer cards. You only want to use nvidia-173 if you've an old card that is not supported by the nvidia-current driver, i.e. the GeForce 5 series.
There is also a nvidia-96 driver for even older cards, the GeForce 2 through 4 series.
LPR is part of the cups-client package - it provides interfaces that allow printing via command line and apparently over the network. It appears the lpr packages provides needed information and utilities, while the cupswrapper packages provide a wrapper for configuring cups (and depend on files from the LPR package being installed).
Most printers should be automatically configured when you plug in the USB as long as CUPS is installed (it looks for information on the printer, such as a PPD file, so it knows how to work with the printer), so you shouldn't need to install third party packages (see N.B.)
Otherwise, you will likely need to install BOTH packages - download the DEB files and install them, either by opening the downloaded files or using the command line - install the LPR file first:
(where ~/Downloads/* is the path to the deb packages in the Downloads folder - you can also use gdebi instead of dpkg -i)
It is also mentioned here that using the driver info for the HL-2170W seems to work (from foomatic - you can install the foomatic packages using the package manager so you don't have to download the files from a website).
The manufacturer's instructions are available here. Similar instructions can be found here, as well as the recommendation to use a tool provided by Brother.
N.B: With some third party packages (not from the ubuntu repositories which you use with apt-get), they may not be well maintained and may use weird packaging methods - e.g. the provided packages appear to be converted using alien from a Redhat/Fedora RPM file, and do not specify dependcies such as bash, the LPR package, etc -->