Tube Amps Watts vs SS amp


Can someone explain is there is a difference between the watts of a tube amp vs vSS amp, Looking to get a tube amp ,but i see that the watts are much less than the SS amps, So how do these Tubes amps with 25 -70 - wpc drive these high end speakers, I have a vintage pair of AR 9s and 2 mcintosh MC2200 amps in mono (400 WPC) to drive these ,what tube amp will power these under 3-4k new or used, Thanks 
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With tube amps it is not all about the advertised wpc, the transformers ,power supplies are the key and the quality .
i have seen a 18 watt parallel SET amp with great monolith transformers destroy a very respectable 100 watt SS amp 
by having big high headroom transformers  that makes all the 
difference in the world.
Its a long road my man. With a thousand explanation your best bet is to try it both and be the judge of it. Realistically and no offense to anyone, even audiophile guys for years and years still bonds with buying new gadgets almost every 1/4 of a year. How do you explain that? My advise to you is make the most of what you feel is good to you. If you find your component singing to you, she is the one.
"i have seen a 18 watt parallel SET amp with great monolith transformers destroy a very respectable 100 watt SS amp"

I have seen 12wpc tube amps destroy Krell KSA-250 Class A amps before they evaporated into the thin air and never seen again...still looking...
Sanders biases his arguments towards his own amps which are admittedly great values in high powered amps. Yes, high powered tube amps waste a lot more energy as heat than an AB SS amp. He is also expressing his opinion with a bias toward driving his electrostatic speakers. He dismisses OTL amps off hand. He is right that you need to use a lot of tubes to reduce the impedance of the output section but once you do so they are every bit as effective at driving electrostats as SS amps. Sanders is right about clipping affecting the sound quality of amps. Power is expensive it is also everything in terms of producing realistic dynamics at comfortably loud volume levels. Boulder has come to the same decision. There is no such thing as too much power and I am inclined to agree. I am also guilty of being attracted to notoriously inefficient loudspeakers. All things being equal you are way better off buying more power than more cables.. Audioman58, transformers do not make power no matter how big they are and no transformer is always better than any transformer. There is no SET amp capable of the kind of visceral dynamic sound close to being realistic. IMHO they make great headphone amps. There is no speaker efficient enough to make a Set amp produce an undistorted 95 db comfortably which is around what is measure in most small jazz clubs. I suppose if you live in an attached condo and can't disturb the neighbors they are fine. Seigan, a 100 watt tube amp clips at exactly the same place as a 100 watt SS amp. But tube amps clip softly while SS amps clip hard. The Tube amp sounds better clipping than the SS amp which may be the major cause of the attraction of tube amps. The tube amp will seem to play louder. But any amp that is not clipping will sound better than an amp that is. You get an amp to POWER your loudspeakers. Power is everything. The more you can afford the better, Tube or SS. 
I'm not an engineer but it's my understanding that if 2 amps are of equal gain they'll be equally loud at equal wattage output. Meaning that you'll likely be ok with a lower wattage tube amp vs a ss that you rarely ever use all those reaerve watts