Find a pair of used JBL LSR 6332 studio monitors. 12" three way with a ruler flat response and great dynamics. Plug the port and EQ to extend the bass. A used pair should be available for around $1000 Euros. Often the tweeters have been mashed in by some visitor to a recording studio. It's easy to replace the tweeters. Many recordings have been mixed and mastered on those speakers, so you get to hear exactly how they were supposed to sound.
https://jblpro.com/en-US/products/lsr6332
https://jblpro.com/en-US/products/lsr6332
I suppose that's why so many 2-way speakers exist with horns to extend down the compression driver/tweeter.
The JBL LSR28P is a perfect illustration of that point. It uses the same tweeter that the LSR32 / LSR6332 3 - Way, but mounts it in a large waveguide and pairs it with a very good 8" woofer. It has a similar ruler flat response, but the directivity is narrowed by the waveguide. The LSR 28P can also be found used for $250 - $400 each. They are my daily drivers along with the JBL 12" sub. Here is a pic of the newer LSR 2328P, P for powered.
https://jblpro.com/en-US/products/lsr2328p
https://jblpro.com/en-US/products/lsr2328p
I would consider this design by @hifijim
https://www.diyaudio.com/community/attachments/lccam-10-3-design-construction-rev2-pdf.1300501/