You can go directly to 8.9 from 8.0 if you're running property management. It's the same code for the Real Estate Module. The only exception is AREF (Advanced Real Estate Forecasting). It's available for 8.0 but not for 8.9 as it did not make the cut date. If you want to run AREF then you need to install 8.10, which you should be doing now any ways. 8.10 IS AVAILABLE so you might as well install it instead of 8.9.