Demo'ing Class A amps, Appreciation Suggestions from those who recently been there

@chorus , 

Are these an accurate photo of your FSM speakers?
http://usr.audioasylum.com/images/3/38319/fsm.com.jpeg

Are you using the 16ohm tap on your speakers when testing?

With FSMs, (I'm not a Tannoy expert - at all) but It's appears (as you are) worth doing more in-depth research on these before buying any amplifier(s). These speakers you have can be a bit picky.  While they seem efficient, doing some quick checking on my end there are repeated suggestions about some struggling with inadequate tube amps to drive these properly, and a few caving in to use "transistors based amps" to get the best out of them. Interesting. Digging some more, now I can see a bit more what brought you to Pass., and why you are reaching out for suggestions. There are more than a few that have matched up the XA-25 in this case. I'd call and talk to Wayne at Pass and again his perspective, first. Then, if you look at any tube amps again, I would look for musical 50w amps before low watt SET, but that's just me reading about your speakers some. More poking around with the Tannoy crew will help . 

Pass is the best. Long term reliability with class A heat can be a problem. Pass uses excellent components which achieve 15 to 20 years of trouble free operation.  Heat becomes a very important factor with class A.  Check the warranties. 

cakyol,
In March I had the Pass XA25 in my system for 2 weeks running
continuously. It never become too warm to keep a hand on.
My tube amp put off 10 times the heat it seems.
I live in Phoenix Arizona.  We know something about heat. 

Pass has said they seldom see a repair issue on their gear.
Further they say that their caps are still good after 20 years.
That is a pretty solid reason to own a Pass.

They are in a state next door to AZ. Another plus.

Finally the XA25 has been marketed for 4 years now. Pass's biggest selling item. Check the Shark resale market right now. Hello New Zealand!! Price has not been raised since the inception $4,900.
As Stan used to say 'Nuff Said'

Chorus,
Okay. Looking over some old notes and references. Interesting, and a completely different direction from low watt.

"High Current Amplifier" with proper drive for the FSMs. 

SET or tube amps with fleawatt grunt isn’t going to cut it on those.

>>The bass driver units require some current to work effectively and sound right<<

Get this, I even found a few instances up to 250w-300w Threshold Monoblocks or high current Accuphase amps being used with FSMs. For testing old used lower cost amps, got any friends around with a recapped/restored Nakamichi PA-7 Stasis amp or Threshold lying around?

Or, closer to new, it woud take a few grand more over your budget, there is a Pass INT-250 in Peoria AZ, closer to you - listed right here on Agon. Bet this would do it. Good luck :)
https://www.audiogon.com/listings/lisa1b8d-pass-labs-int-250-solid-state?refsource=hifishark

Deco,

Yes that is accurate and much better than my avatar, thank you.

They have a bi-wire option on the back.
No choices for different ohms there.

On the front face there is an option to operate the system
as a 2 1/2 way i/o the standard 3 way option.

If you run it as a 2 1/2 way, the impedance changes from 8 ohm to 4 ohm.

I do prefer to listen in the 4 ohm setting. The difference is the upper dual concentric speaker will roll off at the bottom of the mid range when in the Open-4 ohm-setting. When in the Closed -8 ohm-position the same upper mid-range speaker will go all the way down to the 40hz rated bottom. Unless I have this backwards which has been known to happen.

Another feature these speakers have-Three settings each
for the following items: Presence, Roll off, and Energy. 
Gotta love the Brits! Level, -3db or -3db. I use the Level Setting.

I purchased these about 18 months ago. 
I had the caps tested and replaced. One had blown.
Interior wiring upgrade. Plugged a too large compartment
connecting hole. Replaced metal tabs post connectors with stranded
copper wire.

I have had the pleasure of speaking with Kent English at Pass.
Kent has a few larger speakers on dollies. He said that in the Pass
line he felt the XA25 was the best match for my speakers. Over the 250.8 to be precise.  It seems Mr. Pass has worked for magic on this product.

Since this purchase is significant to me I want to do my homework.
Thank you for your help with this.