Lots of folks use lighter bikes and lighter loads, as you say, it must be nice.
My tricross works well with what you intend for September, depending on what load and what wheel set is on yours. The frame handles a good 40lbs reasonably well, although I was careful of my carbon fork and kept front panniers light.
I'm going to load it up and see how I like the ride. I can't see myself packing more than 40lbs for this sort of trip. I do have another set of wheels with more spokes but I ran my credit card tour on 24 spoke lightweight road wheels. The roval wheels on the cross bike look like they might be similar in spoke count too, but I don't have many km on them so we'll see. Cross bikes are pretty versatile though.