The speaker-level input of a powered sub is the input to the sub's amplifier, having very high impedance (probably many thousands of ohms), as opposed to the input of a passive speaker having very low impedance (4 or 8 ohms or thereabouts). Therefore the cable will be conducting miniscule amounts of current, and you don't need a heavy gauge cable that is intended to drive a passive speaker. Also, I would not expect a high degree of correlation between the bass performance of a given cable in a speaker application, and its bass performance in a powered sub application, since the technical factors are so different.
My suggestion is that you research past threads on "subwoofer cables."
Regards,
-- Al
My suggestion is that you research past threads on "subwoofer cables."
Regards,
-- Al