As a follow-up, I have been speaking with IT Solutions (
Exchange Hosting by IT Solutions Now), and was lucky enough to speak with a very helpful Senior Systems Engineer. She took the time to stay in touch via e-mail after a dropped call, and indicated that she would test out the Mac Address Book with their service to see if they could get it to sync. Bear in mind that this is unsupported by everyone (it appears), even though it should work, so she didn't even have to take the time to try it out.
Nevertheless, I received an e-mail this morning indicating that it works. That, coupled with their service/price ratio and their outstanding willingness to work with me on unsupported features, won me over. I'll be signing up with them next week.
I don't have the settings just yet, but once I have an account and have everything working, I'll post the settings for others in the same situation.