VLC sucks for this purpose (it's one of my least favorite players) because it has limited GPU acceleration support, but you can try to use it. To get that minimal support, you have to ensure that you have 'Use GPU Acceleration' checked under Input & Codec Settings. I really don't understand the reason behind VLC's popularity when most people don't even use its real advantages.
KMPlayer does not support DXVA natively, so you have to use an external codec to take advantage of your APU's feature set.
Before you give up, try taking out the codecs that you installed (except for ac3 filter) and put in DiVX. Under Codec Settings, go to Playback Settings. Uncheck everything and check 'Use DXVA hardware accelerated playback when available.' Make sure that your player uses the DivX codec, and see if it works. Chances are, it would.
Enjoy.