Most likely, yes. I would like to say absolutely yes, but you can't say that if you don't actually test it. Component temperatures tend to rise as more power is used, and tend to decrease when less power is used. If the temperature also dropped it's pretty much guarantied that your power consumption dropped.
Lowering the clock speed won't drop power consumption much unless Vcore is dropped too.
I don't know why you don't just use Cool n Quiet, I've got it enabled using Vista and when I choose power saver my Phenom 9850 remains at 1.250Ghz, Balance allows it to automatically scale between that and 3.0Ghz, and Performance leaves it at 3.0Ghz constant.
If I remember correctly, power scales directly with core speed, and directly with voltage squared. So, you have saved some power, and if you decrease the voltage as well (it should run at the lower speed with quite a bit less voltage), you'll decrease the power even more.