Buy a speaker that you don't need adjust or modify,
unless its a inexpensive vintage speaker IMO.
I'm sure it's not intended, but that's not a very helpful or welcoming reply to someone who's asking specifically about building a system around the LS60.
This may not be particularly helpful either (and it's not really a "tweak"), but I had LS50s for quite a while, and I believe that many of their attributes also apply to their big brother.
I'd consider thinking about how to integrate a good subwoofer into your system. I've had great success with a REL Serie /S sub using REL's extremely fast and effective wireless interface. This enables you to place the sub in a location that works both acoustically and from a design standpoint (and I'm guessing that design is important to someone who's selected the LS60).
My REL allows my main speakers to do what they do best (imaging, coherence, tonality, air, etc.), and it doesn't muddy their sound. Even though the sub is located behind and to the right of my primary listening position, it appears that the extended bass and fullness comes from the main speakers in front of me.
Good luck!