Why do you need so much power?

2 watts, 20, 35 watts, etc etc. 

  there is no substitute for headroom, and having the reserves for those crescendos’ / peaks / quiet passages......and the full on massive orchestral frenzy of woodwinds, bass, as the fury of the full orchestra slams you like a ton of bricks,......... you will need the watts, to make the smooth transaction from the small flute, or simple cello, to the full orchestra smash which happens awesomely in classical music.
  Not having the reserve and power to deliver these peaks will result in unhappiness. 
 Speaking from experience. 
https://www.youtube.com/watch?v=Sg14jNbBb-8

 

I have a 4 watt Decware tube amp with 92db Ref 3A de Capos.  Plenty loud in my 12x22 room, listen to rock, blues, folk and jazz
not concert loud

The same reason people drive 250+ horsepower cars - effortless performance. The Emotiva has WAY more power than you will need, so it will never strain. Another BIG factor is that Emotiva's are reasonably priced. I have an 8 wpc amp that costs more than the Emotiva! Your friend wanted you to get a bargain! It will certainly cost less than anything from PASS labs (I have two pass amps, not complaining). By the way 80 watts sounds only about 3X louder than 8 watts. To sound three-ish times louder than 80 watts, you'd need 800! Keep Smiling!

@boomerbillone

The same reason people drive 250+ horsepower cars - effortless performance. The Emotiva has WAY more power than you will need, so it will never strain. Another BIG factor is that Emotiva’s are reasonably priced.

while there is some truth to what you say, i would only add that there is a very important dimension of quality that matters, not just quantity of watts... if the objective is indeed to achieve great sound

Another point - you might look for actual measurements of your Tannoys if you can find them.  Many/most speakers are not nearly as efficient as the manufacturer's specs indicate.  Sometimes, the difference can be as much as 6db.