Not all routers/gateways, provide a method of defining an IP from itself. Which gateway is this? the new hitron?
Personally, i prefer to set it from the device myself.. gives you a little more flexibility too, as you then can define different DNS servers, etc as well just for that device (vs it taking just whatever the gateway has).
You can set a static address, on the PC, so that never changes, and i beleive MOST of the seagate drives will allow this as well.
This way there would be no change when any of them boot up. This is actually BETTER, in the fact that the device is setting it and knows its IP already.. vs it REQUESTING it from the gateway/router, and then having to set them, based on what it receives.