What Power Amplifier Should I Buy?

Try crossing them lower, like much lower, say 60Hz. You're cutting the f208 above the knees by crossing them at 120Hz! I know these speakers well and realize they aren't bass monsters, but you can definitely let them play to 60 or even lower and flush out more punch.

Based on your current setup, it sounds like you're already in a great place with your Bryston 2.5B cubed, but I understand the desire for more power. The 4B cubed would be a solid upgrade, delivering more headroom and dynamic range without sacrificing the Bryston sound you enjoy. Given your listening habits, it will likely provide that extra "oomph" you're seeking without risk of clipping, especially considering your Revel F208's sensitivity and your subwoofer crossover.

If you want to explore alternatives, consider amps like the Pass Labs X250.8 or used McIntosh MC452, both of which are known for high power, clarity, and reliability. Either should fit within your $5K budget used. However, the 4B cubed's synergy with your current system makes it an easy recommendation.

Good luck!

I have two suggestions.

1. If you haven't already, try running your Revels full range and let the subwoofer just handle the lowest frequencies. You will need to set its crossover low - around 40 Hz to achieve this and don't run your Revels run through the sub crossover. You may find that allowing the woofers in the Revels to handle lower frequencies improves the punch factor.

2. The 203's are a fairly difficult load for an amplifier. The Bryston is no slouch but it does not increase its power into lower impedances as well as some other amps (Pass, Krell, Martin Logan, etc.). You might want to look for an amp that is rated to 2 ohms or where the testing shows that power increases substantially into low impedances. These amps are heavy and expensive to build which is why most amps don't perform this way.

I cannot explain why two subwoofers over one increases the soundstage and can improve the imaging (through enlarging the soundstage)… it does. I have heard it, and others commented,  whenever disconnecting one of my two subwoofers when I used them.

Instead of a bigger Bryston get another 2.5B and vertically biamp. I did this to good effect when I had Revel 228 Be. Don’t run them mono, but use each channel of one amp to power the highs and lows of one speaker, or horizontally one amp the highs and one the lows. That said, while the sound may be cleaner and you have a bit more headroom, the difference may not be that huge. You are probably only using a small amount of watts from your existing amp. I found it beneficial overall though, and I don’t listen that loud either.  Only issue is using a y-splitter for your preamp outputs if you don’t have one with two sets of outputs.