@ict-centraal,
If you only run one website, and aren't doing any clustering of ColdFusion and using any of the Enterprise-only features (you'll have to look at one of the feature matrices to see what is Enterprise-only), then you should be fine with Standard. There are a couple of ways to migrate your settings. If you create a CAR file from CF9 Administrator, you should be able to import it into CF11. Just make sure you install CF11 first as a trial (no serial number) and in standalone mode. Then import the CAR, then once all the settings have been migrated correctly, put in the Standard serial number.
-Carl V.