I am a Eurail Global Pass holder. Is RailEurope my only option, if I am to try and purchase all bookings 'under one roof'? Some sites of local operators, as listed by seat61.com, aren't easy to navigate.
According to Mark Smith on his Man in Seat 61 web site (which I have usually found reliable) the issue is that DB only lets you do reservation-seat-only for domestic journeys and you want an international one. Here is more info from his site.