A butt-load spent in cables - how much improvemt?

Vman,
Just do it. No one will laugh.

Depends, as always, on the system. On my recent interim system consisting of my current Wadia, an Ayre AX-7e and B&W 804S speakers (no isolation gear or any of the other stuff I have now) I was using all kinds of low end cable with no issues (bettercables speaker cables, interconnects, Transparent basic Musiclin)k. When I moved up to my current system configuration I nearly went deaf from the horrid sound. I upgraded the cable and all was well. In the end, the improvement was beyond measurement.

Monster cable and power products will make your face melt (and not in the Jack Black good way).

I'm very happy with my current cabling

Me too...I use stock PC's, stock balanced XLR IC's and Monster speaker cable for surround speakers. I do use a power conditioner to get rid of AC line noise and to maintain appropriate voltage and it did make a small difference but apart from that I don't sweat or worry about what kind of copper wires to use between gear or those that connect them to an outlet.

If simpy changing a cable makes a huge difference then it says more about the robustness and matching of the system components themselves than anything else. Good properly matched gear should not change presentation dramatically because of a different piece of appropriately shielded/sized wire that connects it to other components or supplies power to it. Just my two cents.