Assuming that that your CPU and/or GPU is not overheating and/or inappropriately OC'ed there is only one part in your list that is likely causing problems, your power supply! A bad power supply is the single component most likely to cause problems with a performance computer. Check out this list, your PS is in Tier 5, not good!
http://www.eggxpert.com/forums/thread/323050.aspx
The rest is fine although you didn't mention your GPU. If it is simply to low on the GPU totem pole, so to speak, then that could also be a problem!