I too am in the market for new less flattable tires. I ride on 700/23's and have been flatting way too often. Have you considered Armadillos? My son races at a high level and says the guys he trains with all use them for
their training rides knowing wasting time changing flats ultimately shortens the ride time. He says they roll pretty well surprisingly and he can ride through almost anything, including glass without a flat. Anyone on them and liking them???