How juicy is your NAS?

I'm in the market for a NAS/SAN and have been looking at dedicated hardware. In fact I think I'm close to a purchase.

However I know many of you run umpteen different free NAS/SAN solutions. Seeing as I've a rather snazzy 3ware RAID card it seems a shame not to give a free NAS a go.
Thing is while I've all the hardware and can add more HDD's at will I'm concerned about the amount of electric-juice an always-on free NAS drinks.

So a few questions:

• Have any of you tested you NAS setups for power consumption and how does it figure?
• Are you able to configure idle modes for these custom built solutions and how does it affect its consumption?
• What is the reaction time for a free NAS serving services such as Squeezebox and iTunes to requests from WLAN devices in the mood to listen to some tunes?

The UPS reports my HP Microserver with 2x Samsung EcoGreen at 28W idle.

It runs Windows 2008 R2, I have configured the usual Windows power options to spin down the drives, don't know if they ever do or not.

Don't use Squeezebox or iTunes, all my clients are Windows machines using drive mounts, using Intel NICs I get great responsiveness and up to 70-80MB/s transfers. Results are less stellar with other Gigabit NICs.