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

debjit_g,
Line Magnetic is an excellent suggestion for a very high quality tube (Particularly SET as well as push pull) integrated amplifiers. I’d also recommend that you consider the Italian Tektron brand as well. They offer quite a large stable of integrated amplifiers as push pull or SET. This is the brand of amplifiers that Cube Audio always selects in their European audio shows and demonstrations.

I believe that most of their models fall well within your budget range.
Charles

debjit_g, 
Here's another possibility.  The Canadian company Coincident has an integrated amplifier named the Dynamo. It is available in two versions, el 34 or 300b (A bit more expensive but I think excellent for the Nenuphar). Both of these are single end circuits rather than push pull. The latest versions have bigger and  better output transformers and beefed up power supplies. Worth a thought.
Charles 

If you want to stay with your FirstWatt amplifier, I have had excellent results with a tube preamp from Backert. All of their models have very long tube life and are very easy to tube roll (I recommend the Mullard 12au7).

Robert

thanks @stephendunn and @charles1dad. All excellent options and I will do some readings on them.

I remember writing to Tektron USA distributor before I bought the Nenuphars but did not hear back. I didn’t follow through at that time. Maybe its time to do a follow up. Has anybody heard in person how the Nenuphar sounds with the Tektron vs the First Watt or other amps ? I am hoping that the 2A3 can power the Cube’s to a comfortable listening level when the listening position is 8-9ft from the speaker.
I was also considering Triode labs, either a 2A3 or 300B integrated but they don't have a remote which is a deal breaker for me.

@rwpollock, yes I have heard great things about Backert. Which model are you using ? If I go with the tube pre route with the SIT-3, I am also considering Supretek DHT pre. I hope all these choices will be better than the BHK pre (which is no slouch) that I am currently using.

debjit_g
Tektron offers quite a range. Besides 2A3 and 300b they have a 211 tube integrated amplifier. This is pretty unique. Of course they have a plethora of  non DHT pentode type el 34, KT 88,KT 150,6550 models. etc.
Charles