Welcome to the community, Matt @katmaimatt.
After leaving my speaker based Naim system and analog front end behind, I listened with an ND 555 with two 555 PS DR feeding a Woo Audio WA33 headphone amp. After a while it became clear that my listening habits had reached the limits of Naim’s approach to music reproduction. At that point I remembered a stellar system I got to hear in Luxembourg. It consisted of a dCS Paganini stack with Spectral amps and Avalon speakers in a purpose built listening room. Truly delightful. Because of that fond memory I ordered a Bartók with headphone amp plus a Vivaldi clock. The switch was rewarding. Bartók and clock are different from what Naim delivers. In some areas like realism or inner musical structure the new setup was ahead, in others not (e.g. foot tapping quality). Both firms place different emphasis. I didn’t make an interim stop with Rossini and upgraded to Vivaldi after reading enough of the very positive posts here. Now the overall result is superior in almost all regards. Maybe not when it comes to punch or drive. But that might be a pleasing Naim artifact too… Long story short, I encourage you to test listen to the Rossini. The step up from the ND5XS2 should be very obvious. And then you can see whether what you are leaving behind in Naim sound qualities is fine for you.
I use ChordMusic XLR cables to connect Vivaldi DAC and the headphone amp. A reminiscence to the Naim days… Will be looking at alternatives. Probably will procure test cables from Argento and Esprit. Here’s one of the threads on cables: