The Western Digital Caviar Green (WD10EACS) 1TB SATA (3.0Gb/s) harddrive is quite and has low power consumption which makes it great for HTPCs or general media storage. I am currently using 2 in a Guardian Maximus from NewerTech and the combo has been working flawlessly for 2 weeks now. I had a little problem with mis-matched drives, but fixed that with order a matching drive.
The 1TB drive will format down to 931.5Gb and that is plenty of storage for what I use it for. The Guardian Maximus uses matching drives in RAID-1 (Mirror) to keep your data safe. I would not recommend using these drives a the primary boot disk because the speed is only 5400rpm.
I have been waiting for about a year for the price on these drives to drop to a reasonable price for me and I snagged both for $99.99 from Newegg when they were on sale.