IC's and spkr. cable will only give a minimum improvement at best. Save for a sub or a pair of them. Remember you can put the sub wherever it sounds best to you. Very easy to do. When/if you get a sub, position it at your listening position and walk around the room till you find the spot it suits you. Then kneel down, the sound will change from standing to kneeling. EASY.
After all that, if there is a minor adjustment, one wat or another,is the time for checking out cable.
After all that, if there is a minor adjustment, one wat or another,is the time for checking out cable.