Do we really need anything more than 8" woofer and 1" tweeter for medium size room?

Phusis, that's the task for a driver designer to find the best compromise possible. 
Orpheus10, yes coherence is much more important than frequency extention. That's one of the reasons, perhaps the most important one, of why one set-up sounds right even if not at all perfect and another one wrong even if it could sound impressive for the first minute.

8" is too small. Show me a speaker with an 8" driver that goes down to 20hz with less than 5% distortion? Not room gained down to 20hz but real output. 

@james633

Show me music that has that much content below 40 Hz. Show me an affordable speaker that goes down to 20 Hz with measured low distortion. Show me a modest living room that doesn’t have significant room modes below 80 Hz.

So, I think for a lot of people, properly set up, 6" to 8" is a sweet spot.

Is it perfect? No, but, properly set up, it’s magical. For specmanship not so much, but spec’s don’t listen to music.

Getting that last octave right is a challenge financially, aesthetically and effort.

I have a Hsu 15" 1,500 watt subwoofer sitting right next to my main speakers with 6.5" woofers right now. It's not even going to be plugged in until I have guests over for movies. Why? Huge pain in the butt to get right. :) I've experimented and carefully calibrated it for music in the past.  It was honestly a "Meh" experience.

Depends of course on what part of music you want to experience. If that last octave is where you live and breathe of course this would be unnaceptable. 

By the way, these speakers have convincing output to 30 Hz in room and can play much more loudly than I care to listen.

Best,


Erik

Here by the way is a really good 2 way speaker kit with a 10" woofer, would run you around $1k to build it yourself.

https://www.madisoundspeakerstore.com/2-way-speaker-kits/seas-a26-10-2-way-kit-pair-based-on-the-cla...

I have no financial interest in whether anyone here buys them or not, just thought I'd offer it up to any who might be reading. One of the big advantages to building this kit is you can set the treble balance exactly how you like it. :) 

Best,


Erik