How will removing optical drives and floppy drives help?? If you dont use them, they wont consume any power!
If you have another HDD, then yes that will consume power... but less, as it will be "idling".
Btw, your comp isn't exactly idling when its downloading!
Besides setting your display to go into standby, you could fiddle in your bios. See if you have a setting to put "turn off" the slots that are not in use.
I don't think there is anything else you can do for power saving.