6.5 vs 8 vs 10 woofer


IMHO I think the 8 is the ideal size cone for mid/small sized listening rooms. Even for large size listening rooms. 
The lower mid hz's seem cleaner/clearer. And  there is so little fq's in 905+ of the music we listen to, it seems to me the 8  driver is the most perfect size cone.
A 10 size cone  has the potential to become overwheling, aggressive, attacking when amp gain is pushed just a  tad too much, = Better  volume  control with a  8 vs a 10. 
The 6.5 misses some of that lower bass which a  8 can voice superior. 
After listening to several YT vids with a  10 FR, I had considered going 10, but i think  staying with a  8 avoids regrets. 
I listen at low/mid volume. 

mozartfan
I don't know about that OP.  I run

6 12" OB servo subs in 3 columns (GRs)
12 8" MB PP drivers in 4 SAT columns or 2 72" NB columns (Mine)
12 8" planars in 2 74" 420 lb HDF NB Di or Bipole columns (switch flip)
2 AC G1s Tweeters ribbons 6" ribbon
4 AC G2si Tweeters ribbons 2" ribbon (VMPS RMx Elixir cabinets)

36 active drivers

OB = Open Baffle
NB = Narrow Baffle
PP = Phase Plugs
HDF = High Density Fiber
SAT = Stack and Test speaker system

I don't care WHO say it.. More is better when it comes to drivers...

Fully active direct coupled MB columns (8") with full blown DSP, and an active OXO

These 8" drivers work from 60hz to 300hz.. I use 12K Behringers and a 2496. Absolute control. Very good dampening that actually WORKS..
Dampening CAN'T work unless they are direct coupled. NO OX between the driver and the amp. Most folks don't know that...

Getting them ALL to work correctly together, that's a whole different story with this 13 year old project. I'm close.. This year maybe.. :-)

SO 8" X a lot works for me. :-)

Regards
One thing I have learned after all these decades is there are no rules on what designs are the best because there are GREAT designs of every possible description. 
oldhvymec,

You need to take a video with your cell phone so we can validate your approach.  
I think we have a new Kenjit. Very few people can fill those shoes, but we seem to have a winner!
Clearly the OP doesn't list his room size and mention 8" woofer is sufficient for large sized rooms come on. Doug Schroeder hits the nail on the head.