Seeking Rock&Roll Speakers

If you want volume, you should be looking for speakers with a higher sensitivity than the Thiel's which is 87db. Since a 3db increase in sensitivity is the same as doubling amplifier power, a speaker with 93db sensitivity and your amp would be like using a 600w amp on the Thiel's. Look here,

http://www.diyaudio.com/wiki/Loudness_and_Speaker_Sensitivity

The Tyler Pro Dynamics series are high sensitivity, but their other speakers and the Brystons are about the same sensitivity as your Thiel's. Considering that you want volume and using the calculations here,

http://www.daedalusaudio.com/images/loudspeaker%20sensitivity.pdf

an 87db speaker may need as much as 1000 watts on peaks to meet your needs, however a 97db speaker would only need 100 watts. Trying to get volume from a lower sensitivity speaker, it is more likely that the amplifier clips on peaks, causing the distortion.

Take a look at Zu Audio and their liberal return policy,

http://www.zuaudio.com/questions-list/?category=Commerce

I have listened to various Zu speakers, and they will definitely rock, but can also do other music well.

I think I was unclear in my objectives.
My Thiel 2.4s are really great speakers and do 85% of
my music well.
But sometimes, e.g. during a full moon, I get the urge to
just crank it up.
"Wang Dang Sweet Poon-tang" needs to be played LOUD!
I'm looking for some bulletproof mini-gun type speakers
to meet my occasional needs.
Something I can swap with the Thiel's when the mood is right.

BTW: I'm not worried about my amp having enough power,
I'm worried about shredding the 3" coincident driver
and the headaches involved with its repair.

Dweller, you were very clear on your objective, so I will try again. The maximum loudness of a system is determined by the relationship between speaker sensitivity and amplifier power, and this is NOT a linear relationship. If you choose another speaker with 87db sensitivity, regardless of how "bulletproof", it will be damaged just as easy as the Thiels'. With either one, you would likely fry the tweeter, and not damage the midrange and/or woofer. So if you want to play LOUD, with little to no chance of damaging anything, being "bulletproof", as you say, then you need to use a speaker with a high sensitivity.

Hopefully the power calculator in this link will help you understand,

http://www.allegrosound.com/Power_AllegroSound.html

Look at the example just below the calculator using an 87db speaker and that determines a 200w amp is needed for 100db peaks in the music. Now look above the calculator at "Desired SPL" showing rock music at 95-110db. If you plug in the 110db for peaks, your 87db speaker will need over 1900 watts at the 3.5M distance. Now if you use a speaker with 98db sensitivity only 154 watts are needed for those same 110db peaks.

So if you want to "crank it up" and play LOUD, you need to use a high sensitivity speaker for it to be "bulletproof".

Again, look at Zu Audio. As I said, they will definitely rock, and I seriously doubt you will be disappointed.