OPINIONS NEEDED 100 trade-in chance FOCAL

The full-price upgrade option is as good as it gets, so if you want to upgrade, now's the time. But, IMO, if you really want to know if the new speakers work, you need a home demo. Sometimes a bigger, "better" speaker just won't work as well in your room as a smaller one due to the way the room works with the speaker. But if the upgrade works, it's a great deal. Good luck.

Have you questioned how/why she could do this? My guess that this is off full retail of $5000? Even if she gave you your original purchase price off ($1800 or so?) that she still can make money on your upgrade and wind up with a free pair of 726 to resell?
So, your price to get into the 748 would be an additional $3000 or so? Am I close? This is a fair deal if you want badly to upgrade. However, if you consider selling your speakers and applying all of that cash to something else there are a ton of options for around $4,000.

Jump on it ASAP!!!

I would clearly go with the Diablo. The Diablo is an iconic speaker which will always be in demand creating a high resale value. If you go with a new Diablo you should also expect a minimum 10% courtesy discount!

What Elevick said.

If you are making a major new investment, you have a lot of options. Focus on your goals and the bottom line. The dealer is offering just one of many options that might work out best, including staying where you are if you like it already.