75 feet! And with speakers whose impedance, as shown here, is less than 4 ohms in parts of the mid-bass which typically require lots of energy. Ouch!
You need heavy gauge/low resistance, and fairly low inductance per unit length. You also presumably need to keep the price somewhat within the range of sanity.
I would rule out Clear Day on the basis of inadequate gauge for your application, even in double-shotgun configuration. Regarding Crystal Clear, there don't appear to be technical specs at their website, and I have no particular knowledge of their cables or their prices.
OCOS is reputed to be well suited for long lengths, but I believe that 75 feet of it would cost a not so small fortune, especially in its top of the line versions.
Mofi's recommendation of Signal Cable, especially its "Silver Resolution" cable, is likely to be a fine choice IMO, based on the suitability of its specs for your application, on their very fair pricing (although, nevertheless, 75 feet of it would cost a bit more than $2K), on comments I've seen about it, and on my own positive experiences with their power cords and interconnects. And also on Mofi's history of providing excellent recommendations :-)
Hope that helps. Regards,