Seeking Advice on NOS DAC

Low, regarding a USB/SPDIF converter, I use a Audiophilleo2 with the Pure Power supply between my MAC Mini with Pure Music playback to a Bryston BDA-1. They have come up used here on AG ocassionaly. The AP2W/PP should be had for under $400 used. 

I believe your 1V input sensitivity means your amp/amps achieve full output power with a 1V input.  This is relatively low and should work with about any DAC.  To me, the bigger issue is matching impedance if you are adjusting volume with a passive device.  This can be a significant issue and is probably why I am an advocate of preamps, even though mine is adjusted for unity gain (and buffered).
For example, the Jade and the Adagio (both with onboard volume adjustment) output 2V single-ended (rca) and 4V balanced (XLR) with the volume control handled by adjusting the reference voltage, which does not affect the signal.  Only a few high-end manufacturers (I can only think of Metrum and Empirical Audio right now) offer this type of volume adjustment when going sans-preamp - directly from DAC to amplifier. 
How do you adjust your volume if your DAC directly feeds your tube amp?

I believe your 1V input sensitivity means your amp/amps achieve full output power with a 1V input.

@mitch2 , that's correct; 1V at full power. Regarding the Hex (2V unbalanced), I'm sure it will be a fine match as far as impedance and amp input sensitivity.
Let me give you the back-story, I'm using a PS Audio Nuwave DSD with 2.8V output and I believe it is driving my amp into clipping (sounds like distortion thru speakers). I have a thread posted about jitter control in which several members stated that I'm experiencing clipping due to the low 1.0V input to the amp. At first I thought the harsh sound was due to jitter, but overdriving the amp makes the most sense since it only happens on loud passages, such as a crescendo and close-mic'd brass.
My amp has a nice feature, a direct input with variable gain control; but only up to 1V max. Input impedance is 100 kohms.

I have an Atma-Sphere SE preamp that I take in and out of the system, and there is the same distortion sound during loud passages.
I actually checked other SE tube amps such as Quicksilver and CJ and they have 1.0 input sens. I guess when paired with a preamp with the right amount of gain, it works well.

I have been looking for a NOS DAC with analogue VC and haven't seen a suitable one yet. As far as the Jade and the Adagio, they would be ideal, but none are listed yet in the used market.
I appreciate you keeping up with me on this thread.

Thanks @mesch . And now Schiit makes a converter.

You should check out the new tube dac on the Doge site.  It's probably not NOS, but if it's related to the Doge6 CD player topology, I'm sure it sounds warm and grainless, which is what people who are looking for NOS dacs are usually trying to achieve.  BTW, IMO, looking for a dac based on circuit topology is not the best way to go about it.  Buy for sound, not design or specs.  But that's my opinion and, from what I'm reading around here lately, I stand with a very small minority.  Good luck.