If I would buy the e-SATA version of the Sheevaplug and connect it to a 1GBit router and e-SATA hard drive I
would be able to use the e-SATA port for the hard drive and the USB port for the router.

I have a 1GBit router and a 1GBit hard drive. I would like to use the e-SATA port for the hard drive and the USB port for the router.