It does not matter what decoder you use. If it supports the hardware decoder of Intel graphics, that's good, will lower CPU usage, but won't affect EU load. If not, just CPU load will slightly rise, that's it. In the chart, GPU load = EU load. (EU = Execution Unit)
DVD is the most difficult format because it is telecined. It has to be inverse telecined and turned into 23.976fps video stream before SVP. Soft-telecined is actually progressive, so easy. Hard-telecined is difficult and I haven't found a satisfactory solution yet.
A8-6600K + MSI microATX looks good, but the mb lacks HDMI port, you will have to buy this adapter (that supports audio). A10 is too much for HTPC.
Scythe Ninja Mini is still good for A8. Add a good 92mm fan such as ARCTIC F9 PWM, GELID Silent 9 PWM, Noctua NF-A9x14 PWM or Noctua NF-B9 PWM.