Hi Coyote,
I am not going to recommend one setup over another ..... as you know, I enjoy both drivers .....
As to the "on sale" price of the F-15, they have been on sale for a LONG time. I have not heard anything about a premium version.
A while back, they made a cosmetic change and went to an acrylic phase plug instead of the original wood phase plug.
This has been a very successful driver for Lii Audio.
To my ears, the top end of the F-15 is totally adequate with no help.
It plays the upper harmonics of instruments and does things like cymbals and chimes well if the recording is good.
Of course, if the recording is substandard (and many are) .... the cymbals will sound like an aluminum pie pan being whacked on with a broom handle .....
I think that most of the forum readers who own baffles with the F-15 drivers have expressed a similar satisfaction with the top end of the driver.
The 8" drivers definitely need help in the lower bass ..... but in my small baffles the F-15s also benefit from a subwoofer or bass baffle, in my opinion.
In a larger baffle .... the bass is more substantial and needs no help on the bottom.
https://www.decware.com/newsite/ZMS2.htmlhttps://www.decware.com/newsite/ZMS.htmlSome other forum contributors might have some additional thoughts.
Best wishes,
Randy