The 103 cartridge, unless modified, has a finite limit (like all cartridges) to it’s capacity for expressing nuance. the denon 103 is known for it’s self noise which blurs and covers up detail. That is why so many modified versions based on the 103 exist out there in the wild.
therefore, look to a new expression of a 103, a modified 103, an altered ’lower self noise’ version of a 103, and then you will get more from the Auditorium 23 SUT that you already have.
The OP might be using a modified 103 or a cart based upon a 103, already, but that is not clear from the OP itself.