Since I was asked to clarify, "significantly more efficient", I guess I will post some hash per watt numbers.

According to litecoin wiki mining hardware comparison, an AMD Phenom X4 955 at 3.6ghz gets 24kh @ 125 watts. This translates to 0.192kh per watt.
A gpu rig consisting of 69xx series gpus can produce 998kh @ 920 watts at the wall. This translates to 1.08kh per watt.

So does at least a 5.6 factor increase in *efficiency* qualify as "significantly more"?

Consider the litecoin wiki entry for the Intel Core i7 860 which produces 25kh at 153 watts (a believable wattage consumption for the entire system). It gives a system kh/watt score of only 0.163. The gpu example is now a factor of 6.6 times more efficient.

PS, Mtrlt has gotten better kh/watt scores by playing with the clocks and voltages, but I figured I would give you an initial test result.