Again, audits are based on the state of your company, not the state of a particular product. If your product isn't on the market in the US and you're not going for ISO registration, I don't see why an audit would be necessary. If you're not fully compliant with all of 820 and/or 13485, a full audit would be rather meaningless. If you do an internal audit of the parts that you're working under, you may get some good info on where to improve.