SF EXTREMA vs SF Cremona M

The Extremas are worth 5000.
There the best monitors i'v heard.
But they need a really powerful amp or mono blocks to sound best.
My friend is using two Meridian 557 amps bridged on the Extremas.
The Skaaning midbase on the Extremas is a Carbon Fiber Polypropelene midbase. This is the best sounding midbase I ever heard. It has a richness and imaging that no other midbase has. I like it better then the new Skaaning midbases which are 100 percent Polypropelene.
The Extremas also use the Dynaudio Esotar tweeter which is a great tweeter.
I would keep the Extremas.

I got another offer to swap SF Elipsa to the SF Extrema then I have to add cash. Is that an upgrade? If yes; how much should I add? Hope to get more advise ... thank you

The common denominator here is that SF enthusiasts want your Extremas and are willing to trade current models to get them. I'd be very cautious about giving them up.

I've heard the Cremona Ms and love them, but based on what I've read, the Extremas have almost another octave of bass extension.