What Power Amplifier Should I Buy?

@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.

@scm I deliberately crossover at 100-120Hz because of a nasty room resonance at 40Hz. This creates a big dip at 80Hz that can't be EQed away very effectively. This dip is very strong with the f208 speakers. It is much smaller with the sub. I've placed the XO frequency a reasonable distance from that resonance. I've used REW and other tools to guide me.

I've listened to sub only at 75, 100, and 120 Hz. I cannot hear voices at all. Frequencies below 200 Hz are radiated into a half sphere, with no dependence on angle. How can this muddy the sound?

Of course, I could be wrong. Could you explain how this higher XO frequency creates muddiness? Thanks.

Two subs may be the way to go.