Overkill for small room

I have a smaller room than yours and am running Fritz Rev7 SEs.  They have a similar size footprint, woofer, frequency response, as well as being rear ported.  I know it’s not the same speaker but I do not think you will overload the room with bass.  My room is not.  I’ve even added two subs to my setup and it still doesn’t overload the room.  I have some decent treatment though.  I think you will be fine.  You can also plug the rear port if you like and see what that does.  I plugged mine with some memory foam inserts I made myself.  Good amplification with a good damping factor would help bring you nice tight bass.

Here is a good explanation of damping factor

https://us.kef.com/blogs/news/damping-factor-explained#:~:text=Damping%20factor%20is%20a%20specification,quick%20tutorial%20is%20in%20order.

It is a combination of the amp and speaker and it applies regardless of woofer size. I believe you have the correct general understanding.  I’m no expert on it though. Others here might have better insight.  

Good advice about room treatment.  I would suggest getting a mic and using something like REW to measure your room before treating it, and measure after treatment installation.  Or you could use dsp or Dirac or some other digital room correction.  I have no experience with either of the last two.  I have used a mic and REW and that was straight forward.  I assume dsp and Dirac are as well.

There are many great integrated amps out there.  You don’t need to do separates, particularly if that is cost prohibitive.