Our extensions for Magento can be installed in every shop. It does not make any difference whether you start a new shop from scratch or if you have already a shop running.
Works well out of the box with CE1.9.2. Good documentation and great support. Automated set up is spot on. You may find you want to delete existing tax zone rates in which case this little module will help you https://github.com/GetCommerce/Magento-Mass-Delete-Magento-Tax-Zones-Rates