I am not sure how you could increase base with speaker cables unless you filtered the mid and high range.
In general, if loudness, EQ, room placement or a bigger amp can't do enough for your bass then I would suggest that the only practical way to get more base is to get a speaker with greater bandwidth or a sub (usually this means a bigger box).
A good sub can significantly improve bookshelf speakers bandwidth and fill a low end hole especially at low levels, however, there is still lots of energy in the 80 to 300 Hz range that a small speaker will have to deliver, which leads to a risk of higher distortion at higher listening levels as the small woofer excursion becomes excessive and ultimately unable to keep up with the sub output.
In general, if loudness, EQ, room placement or a bigger amp can't do enough for your bass then I would suggest that the only practical way to get more base is to get a speaker with greater bandwidth or a sub (usually this means a bigger box).
A good sub can significantly improve bookshelf speakers bandwidth and fill a low end hole especially at low levels, however, there is still lots of energy in the 80 to 300 Hz range that a small speaker will have to deliver, which leads to a risk of higher distortion at higher listening levels as the small woofer excursion becomes excessive and ultimately unable to keep up with the sub output.