I bought the 208 after hearing both for many hours. The 208 is Vety cohesive with very good tight bass to under 30 hz in room.
The mid bass gives that jump factor . The 206 even with my subs just were a bit thin compared for the mid bass gives music it's soul.
And the 208 has adjustable bass and treble on the back of the speaker.
If you are in an apartment I can understand,but not in a house .
You do heed 300 hours to fully run these in. Thr x206 is still a very good speaker ,only when put side by side is it thin a bit in the midbass.
With the sub if you crossover around 90 hz then not a problem
But should have 2 subs for even sound pressure.
With Vacuum tube usedjy a Rogue Atlas Magnum 100 wpc which gets over 90 DBS in room ,these speakers are warm ,the tube amp really makes things bid and rich sounding ,for a Rock I prefer my 550 Krell integrated
Much more dynamic control.