Matching Speaker Watts with Amp Watts!

I am looking for a new speaker for my Peavey Bandit. The amp is SS, rated at 80 Watts RMS. The current speaker is a Sheffield 1230 rated at 75 Watts RMS. In my research on the web, one writer recommended that speakers should be rated at 1.5 - 2 times the rating of the amp (to ensure that they don't blow). In a post on this forum, I see that Vaughn recommended an ET65 for a Bandit saying that would work fine. I was thinking that I might need an ET90 to ensure that it can handle the max power from the amp. I'm quite happy to go for the ET65 if that will do the job but I don't understand the rationale behind it. Does it also make a difference if it is a SS versus tube amp? 

It would also be interesting to know if I would get a tone benefit by going with the ET90 and how much the ET90 weighs. The Sheffield speaker is 11 pounds.

NOTE 1:
From some further internet reading, I found a post that made the point that it is rare to drive a speaker at maximum output from the amp for any period of time so it is quite common and relatively safe to have a speaker rated below the max output of the amp. Speakers are made to handle peaks significantly higher than the RMS rating and that would be much more normal than continuous max output levels. That is probably the answer to my question about how safe it is to use an ET65 but the other questions are still relevant.

Note 2:
Well, this may now be academic. I did some more listening and reading and decided to go with the Retro 30. I liked what I heard and what other people said about the Retro 30. I ordered one this evening and now will wait anxiously for Fedex to arrive. Be that as it may, I believe that there is interest in knowing more about the ET90 and hearing some head-to-head comparison with the ET65. 

Chris