Thank you all for your responses. I did some serious (and very, very subjective...) experimenting last few days.
Well, I did try Reference 3A jumpers, direct coupling (behind the plate) with the existing cable inside the speaker, Nordost Norse jumpers, and 99.997% silver wire, braided. No shielding.
Tried to connect on the traditional way, (+) on the LF driver and (-) to the HF driver...
Did not try WA Silver jumpers.
Best results are with braided silver wire, straight to the binding posts (no connector of any kind, just crimped by the post) with main wire connected to the LF driver.
Best of all, I had this wire as a leftover from the another project. Few years ago I rewired one of my Fender Strats with silver, with surprisingly good results.
Since this wire was free and WA SJ are $315 (I think) - I did not even try to get WA jumpers.
Maybe one day.
How does it sounds? The best HF extension, by far, and not etched at all. Mids are better quite a bit than Nordost, which was the best of all - except silver, of course.
Most of all, silver has that "air" added, in a very good way.
I could bet that even LF became tigher, more controlled.
As always, YMMV. I know I like silver, but not enough to get second mortgage to get all my cabling silver. For sensible audiomaniacs out there, if you have Reference 3A speakers, check out their cables. But, don't stop there.