The right voice talent will bring more than a pleasing sound. Virtually all products are edited. Allow 10 hours of studio and editing time for an hour of finished tape. If you're out in four you can congratulate yourself, and apply the money saved to marketing. Taking your title to CD is easy enough technically.
Sales are growing for CDs, however cassettes are still the most versatile and popular format.
A distributor is a volume over percentage of sale decision. A distributor's job is to sell your title into as many places as possible, including stores and catalogs. You need an audio distributor, especially for fiction. Use an established audio distributor who has relationships and regular contact with the decision makers at catalogs, the chain stores and libraries. Ask colleagues who they're working with.