I absolutely disagree, I have heard every one of those drivers and I owned personally, the Focal 165k2p and 130kp, boston Z6 and Boston Pro60. I just demo-ed all those components yesterday and I must say that there are different characteristics for each driver.
I am using the Focals now but will be switching back to the Z6's. Focals sound great when you get them, better when they are broken in, but over time they go downhill fast. I confirmed it with my buddy that has had all the components on display for a very long time now.
When I first listened to decide Focal or Boston, the focals sounded the best. Now the exact same drivers are in the exact same config with no changes and the boston clearly beats them out in all aspects.
BostonZ6-in your face sound, more live and good for all types of muisic. 3ohm instead of 4ohm which can give them more power from your amp if its not regulated. Very good Bass responce and very high power handling 50-400 watts. in a test on a board you can hear the difference in output and the impact of the music. It has a more robust sound to it. Voices seem to play right in front of your face and the others seem further away. Brighter tweeter but not at all in a bad way...I beat these things to hell and back and they never even broke a sweat. Oh and they played cleanly and never got drowned out by 4- JL 12w6v2's, even when I ported 2 of them.
PolksSR6000-slightly better bass response than the boston but the midrange is lacking that in your face effect as the Z6. Still an exellent sounding set of drivers and very good SQ guy sound(flat). The highs are smooth as silk but just not my taste. Very highly rated. good power handling but still half the Z6. I did hear them in my buddies ford Ranger and they sound great...but he is an SQ guy with the polks and 1-8w7 sub. But its very clean
Focals-good midrange the highs are a bit too bright when the components start to go like they did for me. the mid starts to go or the highs get brighter...I believe it was the mid. I was happy with them after I broke them in but very worried about long term reliability. Lower power handling than polk or boston. 140-160max
pro60- I hated these..very bright. I mean very bright. I blew a set shortly after having them. They can only take I believe 125RMS watts. I did have 250 watts at 3ohm. I did a comparison with MBQuarts (which are tipically bright) and the Z6. They dont even compare in any way....
I believe its better to have the bostonZ6 that may not play as flat polk and slightly less deep than the polks, but it sounds more dynamic. Listen to them with some video and a good war movie like "when we were soldiers". you will think you are the one being shot at by charlie. You can always eq your components to take away sound. But, more stressing situations like street beating around like I like to do sometimes, you need a very durable driver that wont sweat due to the pressure....Z6 all the way....But I am one of those guys that uses the oscilloscope to get the perfect - super - hot signal to my amps.If they can take 8 volts I feed them 7.99 just to ensure cliping isnt present and I feed as much power as I safely can. I listen to everything from Ozzy to young Jeezy to Michael Jackson to Korn. And everything in between.(Jazz, rock, oldies,etc)
Just my .$.02
do it right the first time ....or do it again and again and again...