In order to use the Horn Management System, you'll need a Speakon cable that uses all 4 poles. If the HMS doesn't matter to you, any thinkc gauge Speakon cable should work, as long as it' wired correctly (there should be a wiring diagram on the back of the amp).
Thanks,
I looked up the cab manual and I believe it comes with a correct cable so if I'll see afterwards (if I purchase the cab) if I feel the need to upgrade.
If you're buying them as a package they ought to throw in a 4 wire speaker cable for you for their little built in tweeter amp. Not sure what you mean by upgrade. Spending a few bucks for quality plugs makes sense, spending money on "magic wire" is stupid, don't get taken in by that when a piece of lampcord will perform the exact same function.