Cube Audio Nenuphar Single Driver Speaker (10 inch) TQWT Enclosure

@yorkshireman,
I can not say with any authority that a lower power amplifier would unequivocally be better, certainly as good. @david_ten is enjoying truly splendid results with his superb 2A3 SET . I feel more strongly that the absolute quality of the amplifier is priority number 1.

 The best quality SET you feel that you can afford. SET circuits are straightforward and no mystery. Key criteria are high quality parts, output transformers and very stout power supply. The Nenuphar will readily exploit these amplifier attributes.
Charles 

As far as specific recommendations go there are no shortage of worthy candidates. Have you determined a budget comfort range?
300b SET are more plentiful and are also generally more expensive than 2A3 SET amplifiers. Again, depends on what level/tier of quality you seek. The better the amplifier,  the better the Nenuphar will sound. 

Charles

Thanks again... 

@charles1dad

The amp is an Allnic T1500

http://allnicaudio.com/product/t-1500-mk2/

I think without going up to Kondo, Shindo, Tron, separates a secondhand integrated is about where my budget ends which is at around £3500 GBP - $5000 USD

Do you think this would be high enough quality?

@yorkshireman, 
Just saw your post (Watching the NBA champion game😊). 
I believe that the Allnic is an excellent choice. 

1Established and highly respected manufacturer. 
2 High standard built quality chassis construction. 
3 Very high quality output transformers.
4 Robust power supply.
5 Very thoughtful  soft start mechanism. 

This should sound quite wonderful paired with the Nenuphars. 
When you're able/willing to, buy the best 300b tubes you can afford. 
The one drawback to the 300b is the premium level choices are not low cost. In this case you get what you pay for.  

With an SET of this caliber and the high level Nenuphars there's little rationale for compromising on 300b tube quality.  You'll be rewarded.
Charles