Hitachi's Deskstar 7K1000 drive is available, at least in Austria and Germany, for about €399. This is not exactly a 1TB drive as its capacity is only 1,000GB. For a real TeraByte you need 1,024GB but lets not be the bean pickers.
The hard drive has four platters with 250GB each and it has total of 32MB cache .
It is twice as expensive compared to what you'd have to pay for 2x500GB drives, but it is up to you to go for it.
You can order one here.