interesting discussion.
I am actually using "fancy" $170 or was it $300 cables my friend bought long time ago and gave them to me. Now he is taking them back and I am perfectly OK buying the 14AWG monoprice or similar cables. I am not a believer in cables.
I do however think that 2 biggest improvements can be room treatment and 2nd sub. Specifically 2nd sub.... why? Because I notice that if I move my ass exactly 2 feet to the right, I can feel more sub. So clearly bass is not distributed evenly in the room and maybe 2nd sub will help in evolving the sweet spot. Right?