What do you wish to do? Burn mastered audio CDs?
Do you have Toast? Toast works well. But if you are looking for a more professional audio authoring app you can look at Wavelab, but it does come at a price.
Do you do all your mastering in ProTools, or are you looking at getting a dedicated audio mastering/burning application?
If you do your mastering in ProTools, then you could easily use Toast to burn your finalized audio to CD.