You will want to use a compatable sample rate depending on what you are planning to do. If you are using Adats at 48kHz, you will need to use 48kHz. If you plan to mixdown to CD on the same computer, you will need to use 44.1kHz. Sonar does not have the capability of changing sample rates after a project is started, and it will only create a mixdown file at the same sample rate as the project, so if you would need to convert sample rates, you'll need to use an external application (typically a 2-track editor) after you create the mixdown file.