You probably won't notice much difference due to it still sucking the same volts. Unless you change these, I don't see it getting much lower. Unless its different with graphics cards vs cpu's and ram.
If you really (seriously) want to bring down your GPU temps - get an aftermarket cooler. Is the fan 100%? You can also try putting some quality goop on the vid card heatsink, but again this probably won't get you much. These are your options.
I found that changing from stock clocks to the minimum clocks only used 2 to 3 less Watts at the wall socket.
So there wont be much difference in temps at idle.