The CX is there lower end models. All are made by CWT. Good supplies but a little lower quality then the TX and AX models.
The GS, same as above but they slap a blue fan in them. Made by CWT.
The TX is a little higher quality and are made by Seasonic or CWT, depending on the model.
Then you have the HX and AX and AXi which are higher quality then the CX and GS and TX. The HX are made by Seasonic or CWT depending on the model. The AX are made by Seasonic. The AXi are made by Flextronics.