This is my current build:

EVGA X58 (first generation) motherboard  
Intel i7 965 clocked @ 3.3 Ghz  
3x DDR3-1600 Corsair RAM at stock timings and voltages  
Corsair AX750 80 Plus Gold PSU  
1 Optical Drive  
1 Seagate 7200.10 500 GB drive  
2x Western Digital Caviar Black 1 TB drives  
OCZ Vertex 1 60 GB  
EVGA GTX 460 oc'd at 800/1600/1850   
Antec 1200 case  
HT-Omega Striker 7.1 Sound Card

Windows 7 32-bit Professional (PAE Enabled)

I've already seen this post Reduce power use on computer and this post How do I lower power consumption of my computer and while useful, I'm looking for answers specific to my build and OS.

I'm pretty sure this build is a energy-intensive build by default, but I want to try to reduce the amount of energy my build uses when I leave it idle (when I go to bed or go out, etc). The first requirement for this machine is that I need to leave it on, so I cannot turn it off while it's being unused. I run it as a file server for personal reasons and I also leave it on in case people leave me messages on various IM services and chat clients (IRC, MSN, Steam, XFire, Pidgin, etc). I'm also unable to replace the parts in my computer with a cheaper "greener" part.

What are some ways to minimize the amount of power the machine uses? I'm already using a high efficiency power supply (80 Plus Gold), but I imagine there's other things that can be done in the BIOS and Windows' power settings to reduce power usage while I'm not using the computer. From what I can tell, I can't use Sleep since that'll disable network access (whole reason why I leave the computer on in the first place).

I already turn off my monitor when it's not in use. I enabled Intel SpeedStep within the BIOS (I know, I have a 965 and why am I enabling SpeedStep?) Should I bring the graphics card back to stock speeds and lower the clock on the processor even more?

Main reason why I'm asking is I think this computer alone is the reason why my power bill is high, so I want to reduce its consumption to as low as possible without having to shut the thing down.