flyingwysiwyg,
Before you buy one of those brown box cards check the cooling solution (Many OEM cooling solutions are substandard) and the warranty. Also check for empty solder points on the cards. (Usually those cards are stripped bare.)
Last thing look at the picture from the card when it is running, both in 2-D and 3-D modes. (OEM Cards can have cheaper filters on them that give a poorer image especially in 2-D.)
In the end, do your homework before you buy.
Take Care,
Richard