Your NAT Audio HPS amplifier is very intriguing. NAT has a reputation for their own in house high quality output transformers. Their electronics are highly regarded. Your amplifier to my understanding is 50 watt SET via the GM 70 tube but can be switched to 15 watt power mode. I'm very curious as to which power mode you'll find to sound better with the Nenuphar. NAT is a proven audio product beyond any shadow of doubt. I think that you are in store for quite an exceptional musical journey.
Charles