Lee, I agree with Ron on this issue. After hearing both setups, I found no meaningful performance difference between the Premier with the Director versus the Premier equipped with the Pro ISL module but without the Director.That could be down to how resolving the system is that you heard it on. The system I heard was Magico M3s and it was not subtle.
If I were considering an upgrade path for the Premier, I'd focus on finding a used Reference unit or, even better, move up to a Select 2 like @itay123 did. Or if one have the resources, go for the Cascade. other of those approaches would deliver more substantial improvements than the Director addition.