SET amp comparable to First Watt SIT 1?

We have a number of customers with that speaker that really like the combination. They use either the S-30 or M-60.

Due to the efficiency of the speaker, low distortion at low power is really important and this is why SETs are often preferred. Because our amps don't have a dedicated separate circuit for phase inversion, they too make unmeasurable distortion at lower power levels, and at higher powers considerably less than either the basic SIT amp or an SET (the latter usually being about 10% at full power).

The advantage of the SIT semiconductor is that it has the linearity of a triode including the soft clipping characteristic. That makes it pretty attractive! The problem of course it that they aren't available- all sources now are from NOS stock or robbed from old Sony V-FET amps.

The challenge that you have is that at 99 db, its actually possible to run many SETs into a considerable percentage of full power. If you are pushing it past about 20% of full power, then you won't be really hearing the best out of the amp has it will start to take on a 'loud enough' (shouty) quality (which is why many SET users say that 7 watts is enough power (because the system starts to sound loud; a system without appreciable distortion will not sound loud), until they hear what the same speaker sounds like with more power behind it. So the SIT amp will have an advantage in that regard.

If you are getting the big Volti with the self-powered woofer, then you will be able to get along with 7 watts or so as long as you are using an active crossover. Then a 7-watt SET will make more sense as long as the room is not too big.

I agree with Charles and the other comments. My recommendation about Border Patrol was three-fold: (1) it is made in Maryland and therefore repairs are easy (my recent experience with my Ancient Audio taught me that lesson, but that is another story), (2) Gary Dewes makes only 300b amps (SET, PSET, and PP), and (3) he occasionally sells pre-owned and he might be persuaded to let you have an in-home audition. Compared to the 45 and 2a3 SET amps that I tried, I found my 300b amp to be more dependent on the specific 300b tube that is used. Takatsuki trumped Sophia RP (by a lot) that trumped Shuguang BT (also by a lot), etc.

Per atmaspere's comments- I run 95-96dB open baffle speakers in a moderate size room (14'x23'x8.5') and acoustic/american/fold/country music and found that it was very easy to drive a 7-8w 300b SET or a 10-11w EL-34 SET into that higher distortion zone that he talks about, if I ran the volume up to more than moderate levels.  If your room is not too big and you don't listen very loud, you MIGHT be OK  w a 300b.  If you are a classical music listener, the wider dynamic range will definitely run a 300b amp into clipping.  I switched to a 30 wpc OTL amp and the improvement was dramatic.  OTOH, if you want to give the SET route a try, drop me a p.m.  I have a very good one that is looking for a new home. 

Tmare,
If at all possible I'd strongly urge you to directly compare a high quality 300b SET to an Atma-sphere amplifier and judge for yourself.  I've done this myself. Both amplifiers were very good but certainly  with different presentations. I preferred the 300b SET sound and the obvious point is opinions/preferences will of course vary.

I believe that either choice has excellent potential with your Volti speakers.
Charles

In Linear Tube Audio amps sounded very good to me at Capital Audiofest this past summer for very reasonable cost.  These use some proprietary output transformer magic  (David BEerning ZOTL technology)  in place of a traditional output transformer.    Models I see range from just a few to 40 or so watts per channel.