What Power Amplifier Should I Buy?

 

I never heard the A21, but I was very impressed with the A21+. For the cost it was an excellent amp. I sold that to get the CODA #8 and thought it was more detailed and as powerful as the A21+. I now have the CODA #16 which is better than the #8. The Benchmark LA4 with the Parsound is a great combo. The Holo Serene preamp is another similar option.

The A21+ was disappointing for me. It produced plenty of grunt but otherwise I found it inferior to a 20-year-old OG A21 I had at the time. The A21 was/is considerably quieter and cleaner sounding. I suspect that’s the real reason for why the 21+ is not THX certified despite its claimed specs. The original 21 was measured by Miller Audio Research lab back in 2011. Other than maximum unclipped power, it posted better numbers than the 21+ did in Stereophile’s measurements. 
 

I agree the Coda No.8 is more detailed—it has a lower noise floor than most amplifiers I’ve tried, which probably contributes to that detail. By comparison, the A21 is a little rolled off in the top octave, but on balance, I ultimately preferred the A21 for the way it “effortlessly” went about controlling the speakers, which I didn’t quite get from the No.8. I consider the two amplifiers roughly equal in subjective performance, but the No.8 sells for over 2X the money on the secondhand market, so in that sense I consider the 21 the better value, especially for tougher speaker loads. The difference in outright power between the 21 and No.8 becomes much more apparent on speakers like Magnepans. 
 

The potential downside of the A21 is that its inherently laidback character makes compulsory the use of transparent upstream components, like the Holo Serene you mentioned. That is, if the system’s speakers are voiced neutral or warm. 

@kevemaher 

One likelihood (based on my experience with F208s) is that your current amplification already outclasses your Revels. In other words, the speakers are likely a bigger bottleneck in the grand scheme. The 208s are nice speakers at their price point, but you’d likely get more “bang for your buck” by saving money toward a pair of pre-owned Salon 2s or others of similar clout.

IME, even a mid-tier integrated amp can scale up surprisingly well with >/=$10K speakers. I realized regrettably late in this game that loudspeakers are the major bottleneck in probably 90% of audiophile systems, even when a relatively humble amplifier is employed. For example, I am quite certain I’d rather be stuck on the proverbial “desert island” with my Børresen X3s and Yamaha integrated than with Revel 208s and cost-no-object separates. 
 

…just something to consider 🫣
 

I have three ideas for you but one was already mentioned. Adding a second complimentary subwoofer would help. It's adding more watts, more sound and also taking some load off your main amp (which you like). When I did this, it really opened up the overall soundstage and I felt more amp was producing more realistic organic sound. The second idea I offer is to do the first thing (add second subwoofer that is the same model) and add mono amps of the kind you have. Bryston makes good amps, and if they offer mono amps, I think that would keep that good sound you stated you like. Third idea is to change speakers. I know this maybe a less popular idea, but the facts are some speakers are MUCH easier to drive than others and still sound great. I have had my share of speakers and that is simply an easy solution. Good luck.

Two things come to mind.  The vintage pre-amp may not be up to the task. Ensure that you choose a preamplifier with 2 outputs.  Ultimately consider bi-amping, running the Bryston's on the low-end and something else on the tweeters.  Could be another stereo amp or monoblocs?  You have options with the Bryston's like "jimmy2615" stated.

@jimmy2615   @perazzi28 

I've talked to Bryston about bi-amping. They recomment against doing it because the speakers drop below 4 ohms at the xover to the highs (2.2 KHz), although they hedged saying I moght be OK because there's not much power/current needed at that frequency.

I'm not taking that chance.

Biamping will give me more power only if I use two outputs from the preamp. Not very many preamps have two (balanced) outputs. The ML 38s doesn't. But the Bryston BP-17 cubed does!

What's the word on this preamp? I've looked at it before thinking I would try it or the Benchmark LA-4. I wound up getting a Cary tube power amp. That didn't change the sound very much, so I went back to the Bryston amp.