I'm glad to hear you're having good experiences with Schwalbe support now. I had a very good experience with them last year as they helped me out with a replacement when I ripped the sidewall of a Marathon Supreme tire on its first ride.
You could try the Kojaks. I don't have any experience with them, but they seem like a good fit for what you want except that apparently the lettering is reflective or something. I doubt they'd be in the same league as the Ultremos, but they're supposed to roll pretty well for a touring/city tire.
Is your rim 23mm interior width or exterior? If exterior, I definitely would have expected the 28s to work with that. I've been using 700x25 tires with Velocity A23s and had no problems. If interior, well that's a good bit wider.