They are all 650 watt Gold, they have very little differences that I can see. The 2 with ECO mode available are $15-$25 higher, it is really hard to determine the exact differences. Just was trying to figure out what the fan uses in power, since ECO mode appears to only control when fan comes on or off. Models are like GS, G1 & G2. Some claim to be Nexgen ready, Nvidia something, and some other claims. I think it has to do with what power is available at different voltages???