Sure, there are plenty of 700c tires to choose from, but how many of them are wide enough that you'd consider them a 29er. This may seem like a matter of semantics, but if you're buying a 29er because of the way it rolls over rough pavement, you probably want a wide tire. Of course, there are still a number of good choices for a 29er, but that number is probably around 10.

Anyway, if you are interested in a tire that rolls comfortably over rough pavement, it seems to me that a fat, slick 26 inch tire does that better than a relatively skinny 700c tire. And if you're after a nice mix of comfort and quick acceleration, I think a 26x2.0 Marathon Supreme may be a better choice than a 700x32 Marathon Supreme.