Recommended USB drives for network storage

Hello,

I am on the lookout for a USB drive that I can attach to my wireless router's USB port to use as network-attached storage. My router is capable of this, so the only matter left is to decide on the drive.

My preference is to use a drive that powers itself through the USB port, rather than one that has a separate AC adapter. (I plan to buy the drive the US, where it is cheaper, but use it Europe, where plugging it into a wall socket through an adapter could invalidate my insurance policy -- not a risk I'm willing to take.)

My question is, can the drives that power themselves through the USB cable handle being plugged in 24/7? And if so, is there a particular model that might be particularly well suited to this use? I'm looking for something in the 750-1000 GB range.

Another option is to replace the section of power cable that runs from the adapter brick to the wall with one that ends in a European plug. (That's what I did for my computer, and it cost only 10 cents.) If there is good reason to go with a drive that requires an external AC adapter, can anybody recommend one that comes with a cable that is detachable from the adapter brick?

tx, rh