How long can you wait?, i am assuming you need it asap tho. well my suggestion would be a 570 (maybe 580 if you can squize it in) As for the needs you desire..... you may want to go with a 7870, or a 7950. because a card to handle the games to come for the years to come at full blast is gonna cost more than... 250$
you want to use the card to watch movies and do folding @ home?
Any card will be able to watch movies. And... with the more money you spend on a card, your performance for folding will scale pretty linearly. I am not sure if the folding program you are looking to use is written to play better with AMD or Nvidia cards, but with my experience, OpenCL computing always runs better on AMD cards. For 250 you can pick up a 7850 of your choice brand on newegg. Overclock it as high as the software that comes with will let you - and enjoy your folding. The 7xxx series has quite a reputation for running stable overclocked.