Yikes! Under 6 feet tall and over 90cm PBH? That's some long legs. Literally more than half your height is PBH.
Anyway, a 60cm Appaloosa is a much much bigger bike than a 60cm Schwinn LeTour. The risk is that if you are all legs is that the reach is too far. If your Appaloosa will have a swept back bar, then that's totally manageable. If you've got long arms to go with your long legs that also comes into play, and is not captured by your height.
There is a photo of Roman holding up the PBH range chart. See the phone number on there? Call that and talk it over with them. I predict that after you discuss it with them you'll end up confident in the 60, but that's just my guess. Good luck with your choosing.
Bill Lindsay
El Cerrito, CA