I just put on a set of Schwalbe Marathon Plus 700x25 at 580 g each. I'm surprised at how heavy they feel. I'll try them on a tour and hope they pay off in spares not carried, flats not fixed in the rain, etc.

So why would someone use thorn-resistant tubes with puncture-resistant tires (on the OP's bike)? Sound like belt-and-suspenders. I'm using the lightest tubes I can find with my Schwalbes. Is that a bad idea?