I'm kind of curious abut this idea in that I run the JBL 2435 on top (the commercial variation of the 435BE) bi-amp, XO at 1K. They're rated in their bandpass as a system at 116 dB, 16 ohm, 3 wired in series. I run them individually. I have no idea how to back out an individual sensitivity but I'm guessing it's close to as good as you can do.Given that, I found that 35 WPC SS was not enough - they lack clarity at the volumes I listen, but this is nonetheless in my ~500 ft^2 living room (15 ft cathederal ceiling) so it's not a large space relative to the capabilities of the devices - I'm not stressing them.
I just don't have much faith that 1 or 2 tube watts would do the trick for me, but reading what many people say it certainly ought to. Sort of confusing.