Hm.. weird. I guess then I'd treat those like 25s. The Mondos are more of a racing tire, so they may be closer to a true 23.

Try Michelin Pro Race tires. Even if you don't race, they are nice performing tires. I train and race on mine. They maybe don't have the longest life, but mine are doing fine after a few thousand miles. The back one is looking kind of iffy lately, but I think that's from all the trainer warmups during race season. I run Pro2s still, but the Pro3s are supposed to be more durable. They corner sooo much better than Specialized tires IMO and are pretty good in the wet.

I've also heard good things about Continental 4000 series tires. They are supposed to be pretty bombproof but offer race worthy performance.