If this is a high output design, FaitalPro makes a number of suitable mid/mid-woofers with significantly high output capabilities.
Otherwise, if you aren't looking to shake the house down, ScanSpeak makes some excellent mids and mid woofers.
My listening room is 30 sq. meters. And I dont' want to ruin my house, of course
Thank you for the recommendation.
I'm planning to build a passive system.
18sound 6ND430 4ohm should keep up with your woofer once you factor in baffle step compensation. If running active, 8ohm version is probably better (lower distortion from your amp).
I just started using the 8 ohm version and really lie it. I also just switched to the Wavecor TW030 for a so far so good sensitivity match. An effortless transparent combo.