Is this upgrade worth it?

Hmmm, from yr Electros' spec'd ~220W/8ohm, 1kHz, medium damping you'd be going to ~300W/8ohm, 1kHz, low damping with the MLs. Not much of a power/energy difference, I'm afraid.

Have you ever tried a very powerful amp on these spkrs -- just to compare & contrast "ease of drive" etc. Say a big Crown pro amp -- on loan of course??
I strongly suggest you try this, just to confirm it's the energy that's lacking (or not, as it were).

buy a Pass X350.5 for the same money. a friend sold his 333 for X350.5 and he is a MUCH MUCH happier man now.

Would your friend allow you to hear it in your system?

No i havent tried any hi-current amp's on the speakers,but would love to. .What could make the sound just conk out when it's played a little louder?

Well if he is truely a friend, he would let you hear it in your room w/ your gear for a couple days. Then you would know if it was an upgrade or not. His asking price certainly doesn't say friend, IMHO. Considering most used 333's are selling for under $4K used. Did he spend well over $1K on this alledged upgrade (not including the repair fees)?

It could be me, but I've bought gear from friends, and I've sold gear to friends. We usually get a price discount in the friend's club. If someone wants me to pay more for an item than I could buy the same item for on AudiogoN, I wouldn't consider them a friend as much as I'd consider them a salesman. That's just my humble opinion.

John