What motherboard? How is the Seidon placed in the case? The AMD FX chips get hot and a lot of that heat actually comes from the VRM's. They provide power to the CPU, but if that power is warm, it's already hot going into the chip. When we remove a big copper heat sink and fan from the middle of the motherboard, we remove that cooling that cools the VRM and provides cooler power.
A good board with VRM heatsinks helps, but I found that VRM cooling helps a lot. Even the rear case fan blowing back in to get air moving over them, then exhaust out the top or something.
50 idle is a little weird though.