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

Well... you'd have to experience it to understand it.  

Yes - they do sound as good as virtually any of the full-range speakers out there.  I've compared them.  

Read the reviews - people are replacing their Wilsons, Avantgardes, etc. with these.  

Amazing actually.

This is a very good question indeed. I think it all depends on the type of speaker, the room and what you want to use it for. To answer the question, i think it might be all you need. It depends on the speaker you buy. I have a pair of Wilson audio Duette series 1 speakers that can be very bassy depending on where they are in the room. They dont have sub bass but quality bass. I use them for both music and movies ( just 2 channel no surround sound) in my room and im happy. The room is a bedroom though so that might not qualify as a medium sized room though. It all depends on how far back and how close the speakers are to the side walls. Too far back and far apart they can be boomy!! But bring them out into the room and put them closer together then they will have good bass but not boomy and airy treble with 3d imaging. Thats perfect for music! For movies yea a sub could help out for shure but i dont feel the need to buy a sub. They have an 8 inch woofer and 1 inch soft dome tweeter. The sensitivity rating is 89db. 4ohm speakers. Now lets say they had a 10 inch woofer. That extra 2 inches might make them 6 db’s louder and thats alot! but yes deeper too. I dont want them to be any louder then they are because they are very loud lol. Do i think all speakers with an 8 inch woofer can go as deep as the wilsons? no because of the design of the cabinet, the woofers they use and the crossover design. So listen before you buy. A more affordable speaker with a 10 inch woofer might do what these are doing with an 8 so who knows lol. Also everything matters. The equipment they are connected to can make a difference so choose wisely.

Again, I think it depends on the type of music you normally listen to.  If you came over and sat in front of my system with the Tektons and REL G1 and I played you some Muse and Volbeat at loud levels, then you transport back to your system with what you think is "full range" sound and listen to the same tracks, it wouldn't even be close to the same experience... just not possible.  But that type of music may not be your cup of tea either, which I understand.

If I always only listened to Norah Jones, Mary Black, James Taylor, Michael Buble, etc., then my system would be totally different.

Yes - I not talking about HT movie watching bass or heavy rock bass - just jazz, blues, country, classical, r&b, acoustic bass.

I really don't want my floors and walls to shake - just the sound of a live upright bass, or bass guitar, or live drum kit, etc. - which is what I've got.

There may be no right or wrong answer here.  Everyone makes a good case for their preference.  I have 6.5" full range drivers (SET powered), crossed over to super tweeters at 10k and an 8" sub.   I don't need anything more than the 8" sub.  Within the limitations of the system and room (garage) it has plenty of oomph.  In another system I have speakers with 10" drivers.  I don't need more.  I tried a 12" sub and could plainly hear it down the hall but not at all in the room itself.   But an 8" driver wouldn't be satisfying in that room with my taste in music.  So within the confines of that system and room 10" is optimal.  If I had a dedicated room with full treatments and optimal dimensions I think I would want and need 12" drivers because they are so much fun..