The proprietary drivers are, by leaps and bounds, better in performance. They're not a pain at all though, in both Ubuntu and Linux Mint, simply look for "Device Drivers" in the system menu, and when the card is installed it will have a one click selection for installation.
The sad part about this in general though, is that when it comes to GPUs AMD has better low end and nV has better high end. The nV low end, low price point cards do lag behind the AMD ones, but in Linux you will lag behind more so with AMDs poor Linux support, so the cards I listed above are your best shot.
EDIT: I went and looked up some more reviews on the GT 630....I can NOT suggest that card. It is just a rebranded GT 440, and a very poor performer, even under the Linux drivers. I'm afraid you're likely not going to get anything but shit for your price range. The GT 640 however does show more promise, and is a proper 6 series card using the Kepler core.