The truth on low efficiency speakers like B&W?

I've been learning a lot lately, but I'm still questioning the true amp requirements for speakers such as B&W 802s. I've seen mentions of using 45 watt tube amps all the way up to 600 watt mono blocks. Seriously, what is too little and is a 600 watt amp over kill? Can the speakers ever be pushed hard enough to overcome an amp like the Parasound 2250 with 250 watts/ch @ 8ohms and 400 @ 4 ohms? Is heavy bass music require the upper ends of power? Thanks. Owners please chime in with issues you have had with low power amps.
N802's are not inefficient. They are specified at 90db 1W and 1 meter. They are however, very sensitive to the amplifier driving them and cabling. It is all too easy to end up with a lean, bright sound.

The W4S ST500 is an excellent partner along with a decent tube preamp. A VAC Phi 110 produced excellent bass also. The tube amps will produce a fuller sounding bass with less impact. The VAC pa100 sounds real entertaining with jazz.

The N802's are not the last word in bass definition or tunefulness but one can certainly achieve a good spectral balance and plenty of bass with the right setup.
I can lick my own eyebrows so I went to headphones lately. 600 watts isnt compensation, my 400w amps can shut down during loud complex music on VMPS speakers so 600 could be good if I could afford it.
I've learned the hard way to look carefully at a speakers efficiency rating. A lot of people say buy the speakers and then the amps. This approach doesn't work for me. If you're like me and you've found wonderful tube amps that you just can't live without, then you basically want to find the speakers to match the amps ensuring that neither of their characteristics get in the way of each other. I know a lot of people won't agree....but that's my two cents.

Tube amps are not for every speaker. Tube amps will struggle with highly inefficient speakers.

My general rule of thumb is this: 90db and higher - you are generally fine with tubes or SS or Class-D. 89 db and lower, you better be looking solid state, Class-D or some hybrid (the new Rogue Audio Class-D/Tube hybrids have me intrigued.) That's just my general rule of thumb when shopping.

I'm 100% in the tube camp, so I look for speakers like Sonus Fabers which tend to have wonderful efficiency ratings giving me a plethora of amp options or in my case, letting me use my tube amps.

That's just my opinion. I've found the tube amps I love (McIntosh 2301's married with Gold Lion tubes) and now I have to find the speakers for them!

I think B & W speakers are great, but not efficient.
I can turn my 250 watt Bryston amp on full volume, and It`s not super loud, but  It sounds incredible!
I would never give my B & W`s up, Never!