Hotsyncable Client Data Software Mac to Treo Palm

I have been using a PC with ACT by Sage to manage my client list, appointments, history with clients etc. I book appointments in the office and when traveling often on my Treo Palm PDA.

I would like advice regarding a Mac equivalent for client list management and how to keep the PDA and the Mac synced.

I have a Palm Centro and I have found Missing Sync to work great:

What do you use as the client manager? I'm looking at File Maker 9 but don't know whether that will work or if I even need it. I'm at a disadvantage until I purchase as I don't know whether what comes with it will suffice.