SET amp comparable to First Watt SIT 1?

If you're going to stick to a 300b you do have several options. normally a 300b can only make about 7 watts. You will need more power unless your room is a small one, or if you only listen to light chamber music or solo guitar. Musical peaks take real power! My speakers are 98 db (and don't use a subwoofer but are good to 20 Hz) and I find that 30 watts isn't enough; 60 watts works a lot better. I don't play the system particularly loud either- I just like it to sound as real as possible.

You might consider an Electra Fidelity
http://www.electrafidelity.com/a3-500/
It operates class A3, a class of operation invented by Jack Elliano (who makes the Electra-Print transformers). It offers a few more watts, all of which will be precious when working with a speaker at this level of efficiency. The Class A3 operation also offers lower distortion.

Agree,
The Electra Fidelity 300b SET ìs very good sounding.
I listened to it driving the Cessaro horn speakers in the High Water Sound room for an extended session during CES a few years ago. No doubt that it’s very natural and convincing. It filled a pretty large space with realistic beautiful and engaging music reproduction. Many good SET choices.
Charles

Thank you for more replies. I heard the 2 different types of Volti at different audio shows, and both sounded great to my ears. I have not decided which Volti I would choose. And I’m actually still researching the other horn speaker possibility.

I walked in high end audio world only a few years ago with a rather conventional system (B&W 800D and Classe, etc. ), which I chose based on the store recommendation and the magazine reviews. I still think they are not a horrible choice, but more I listen to the other system, I’m less happy with mine. So this time, I decided to follow my instinct and I’m trying to choose things by my ears as much as possible. The problem is, there are so many interesting equipments on the net, but I have almost no chance to hear them. More I research, I find myself more confused...

Tmare,
You are correct to follow your instincts and simply trusting what you hear. You've discovered the world of lower power  (but high quality) amplifiers and higher efficiency speakers.  This is a very rewarding pathway. In this genre there's a lot of worthy choices and you'll never hear them all. It will all come together in time. Keep reading, learning and listening. 
Charles 

Charles, thank you for your encouragement words.