Power Consumption
You indicated that using a Athlon X2 4850e would save approximately 20 watts compared to using a Athlon 64 X2 7750 processor. The 4850e is rated at a maximum power consumption of 45 Watts compared to the 95 Watts of the 7750. This would appear to save around 40 Watts.
The effect woudl be that the Athlon X2 4850e with the ATI 3300 integrated graphics would draw around 90 Watts under load and less when idle.
You also have another error in that the specific MSI motherborad withATI 3300 integrated graphics includes 1 GB of side port graphics memory which will increase power usage.
Biting the hand that feeds IT
