Bryston 7B3 vs 4B3: Extra Cost Worthwhile?

Yes those Coda 5.5s look very interesting. I thought the same about bridging two. 

@jfrmusic I spoke with Doug at CODA earlier this week on bridging 2 S5.5's for my Yamaha NS5000. He said like most stereo amps bridging is not the optimal way to use the S5.5. He suggested another CODA amp for my speaker. That is a heavy one so not useful for you.

The Benchmark AHB2 is a bit better in regard to bridging a stereo amp. The AHB2 is unfortunately not a the very best match for my NS5000.

@yyzsantabarbara 

Once I get my new streamer and DAC I will give my AHB2 a new audition. Maybe the upper mid lower treble forward  issue I didn’t like was a product of the DAC3. Still waiting for the DAC to arrive at the dealer. Probably this Wednesday. If it sounds better then I might consider getting a second and going bridge mode. But I keep hearing negatives about bridging stereo amps. Right now I haven’t felt completely good about my choices. Although I will be able to audition the 4B3 and the pass x250 at my dealer. And he can deliver to my house. 

@jfrmusic My friend who has an incredible ear, heard my DAC3B and he had issues with the upper mid lower treble forward using the AHB2. We liked the warmer Schitt Yggdrasil+ LIM DAC with this setup. However, when the AHB2 was switched to the warmer Class A CODA #16 we liked the BM DAC3B more. This was with the Yamaha NS5000 speaker which is a bit like the Harbeth 40.1. The AHB2 + Yggdrasil+ LIM was still not perfect with the NS5000. I think it is the drivers of the NS5000 are not the best match for the AHB2.

Here is a little blurb about the ears involved in my home demo.

SR1a (6moons.com)

Interestingly, we both have the BM DAC3 and use it successfully for some purposes.

Here is the content of 2 emails I have from Rory Rail at Benchmark.

Yes, it will work well in your application. The feed-forward error correction keeps the amplifier distortion-free when driving low impedances. (asking about the low impedance Theil CS3.7 speaker)

The amp will sound identical in either mode. In fact, distortion measures the same in either mode. The only difference is that the mono mode plays about 6dB louder.

Best regards,

Rory Rall

Sales Mgr.

Benchmark Media Systems, Inc.

With the AHB2 monos you do suffer some low impedance continuous power. Say running at that impedance for 30 mins. However, your speakers do not dip down there. The distortion is not increased like in other amps doing the same thing. My old Thiel CS3.7 worked OK with the monos, but worked better with a very powerful amp like the CODA #16, Parasound A21+, CODA #8. These are better at low impedance needs. A stereo AHB2 is better than the monos with low impedence but the power tops out around 190 watts at 2 Ohms. My CODA #16 is 600 watts at 2 Ohm in comparison.

@jfrmusic Pass amps operate at about 104-105 degrees Fahrenheit. I own X260.8 monoblocks (previously owned X250.5, XA30.8).
Love these amps with my Wilson Sabrina. However, Pass amps have a warm and natural sound signature. I would not recommend making an assumption Pass and your Harbeth will be a synergistic combination - Harbeths are very warm sounding speakers. If you can go back to Overture and have them set up the same model speakers with Pass for you, it would be best to spend some time listening. 
If you like the sound, the X250.8 will most likely be all you need but it’s up to you if you want to go up to X350.8. I’m pretty sure that amp will never exit out of Class A with your speakers. Have a listen though.