Hmm... Ask me again in 3 weeks cause mine is arriving then.
It has a USB in the back for the pc connection but that will be a USB B (big square one) and the from has a iPod/iPhone compatible USB. The front one 'should' be able to connect to the seagate... I am 90/95% that it can. Although I am not sure on how you would pick the tracks and such.
Martin
EDIT: I just popped on the marantz site and it will connect to an external drive. It may be a but boring but go read through the specs on the web page '
linky'. This is for the UK website but you can find your way to the other site if need be.