You don't need a 2500K (nobody should ever get the vanilla 2500) for video playback. An i3-2100 would be plenty, and you could get something like a 6770 to go with it. Even these would be overkill if you're not gaming.
A good 430W PSU would be plenty for a 6770, or a 500W if you feel like going for something better graphics-wise.
Antec 430W, $40 after rebate: http://www.newegg.com/Product/Product.aspx?Item=N82E16817371034
Antec 500W, $50 after rebate: http://www.newegg.com/Product/Product.aspx?Item=N82E16817371035
If you want this to be a serious gaming rig, let me know. That's where you'll spend as much money as you can put in. For playback, though, even in 3D, you just don't need serious hardware.