Hi Georgehifi> I have read many of your posts here on audiogon. You seem have a lot of knowledge/experience with various amps and how they work. I am using a Bel Canto transport w/B.C. Dac 2. 7 w digital vol. control. B.C. advises for best sound run direct to amp. I have an Arcam A49 int. amp and was thinking of going with their Ref600m or the new E1X amp. I have listened to the Ref 600m amps in another system with different speakers. I have the Focal Kanta 2 speakers in my system. I am getting old now and would like to put together a "last system". I really like transparency and speed and the smaller sized amps are easier to move. But also researching the Benchmark AHB2, Pass XA30.8,PS Audio Signature 250 and Coda TSX last 3 in used market. Any advice/suggestions/opinions will be greatly appreciated. Batman1

Hi  batman1 , I am a "bit" of a fan a the Belcanto Ref600M's Class-D's ever since I heard them on a pair of Raal 2 ways which were a very benign 6ohm flat load and quite efficient, the BC's sounded great into them. But after that the joy was short lived for them into other speakers that have harder impedance/-phase angle loads.

I looked at your Focal Kanta 2 and they look great, save for the very difficult area around  75hz to 180hz where all the power is needed they need big current to sound their best in this bass area

They give amps loadings of 2.9ohms and up to a staggering -75 negative phase angle, these loads I would not wish on any Class-D, tube or even mosfet.
This sort of loading for an amp to drive without any sweat would be better left up to a good bi-polar (bjt) output stage solid sate amp with big hefty power supply, so it can give big current at will into that load, if you want to get the very best from those speakers in the bass.

As for an amp to suggest, yes with the speakers being 91db you don't need a lot of watts >100w@8ohm will do, but current is a must a Gryphon Diablo 120 would be my first choice but it's an integrated.  
Coda TSX looked at their site and they do use bi-polar output stages so these could be good. 

Look for amps that can "double wattage" from 8ohm to 4ohms, and almost double again from 4ohms to 2ohms, this will ensure big current delivery and the amp won't be current starved in that heavy load area.   

Cheers George
Get an Audible Illusions S150 it doubles from 8ohm 150 to 4ohm 300 to
2ohm 600. 
Get an Audible Illusions S150 it doubles from 8ohm 150 to 4ohm 300 to
2ohm 600.
That looks very good for the OP, 150A per channel peak to peak, is there a non-affiliated tests done like from Stereophile, Miller Labs ect to confirm these figures?
Noticed the only discussion on it was removed from Audiogon
Audible Illusions S150 STEREO AMPLIFIER, anyone? - AudiogoN Forums

I don't  know about this integrated but their pre amps have been in stereophile. 
I don't know about this integrated
Isn't the AI S150 a power amp?
Nothing here about it being an integrated. It's a John Curl design and I'm a big advocate of the Parasound  Halo JC1 and now JC1+, bi-polar output big current ability.

Yes batman1 I'd go this also, now I've found it's a JC design, he's the Bi-Polar guru now, NP used to be, but sold out to Mosfets never could understand why, they are more bomb proof, but to me just don't do it compared to his old Thresholds that were Bi-Polar.


Cheers George
Yes, it's a power amp have no idea why I said integrated other than a senior moment.

It will be a real challenge to find "smaller sized amps [that] are easier to move" that genuinely double in output from 4 ohms to 2 ohms.

As Hamlet once said, Ay, there's the rub.

i just looked at pictures of  NAD M22v2..... looks like it has switch mode power supply ...or am i mistaken ?
i just looked at pictures of NAD M22v2..... looks like it has switch mode power supply
Your right 

Cheers George
I can’t speak to the type of power supply.  I just know in my system, it sounds really good connected to my Herron pre-amp.
Thank you to everyone for your responses. After more through investigation on my Arcam A49 int. amp I found the white papers. The G amp produces 200 watt @8ohm then doubles to 400 watts @ 4 ohm. Testing by Stereophile shows approx. 250 watts @8ohm. The white papers make mention of 6 pair of Thermal Trak bipolar output transistors per channel and 60 amperes current. Using a 1.5kva mains transformer. I wanted to use my Bel Canto dac as a volume control and run direct to an amp. But the amp version only was a Stereophile Class A rated amp. So for now with all that is happening I guess I will just sit tight and listen to my super quiet amp. Perhaps sometimes the grass is not always greener on the other side of the fence. Happy listening everyone..