Wife stepping on speaker wire

Her stepping on your cable is indicative of a much deeper problem in your relationship. Her expression of apparent disregard towards your system is a reflection of an underlying jealousy towards what she sees as a rival. The stepping on the cable is an obvious metaphor for her true intent.

Solution(s) - ask her how her day went (actually listen to her reply). If this fails then try flowers and dinner. If still no reaction, then you'll have to go the full monty and buy her a gift equal to cost of your last component upgrade.

No charge!

Get some split loom tubing from your local car stereo shop, etc. This will make the speaker wires look big and provide some limited protection and won't cost much at all.
Here is one web site that has prices and a picture:
http://www.allelectronics.com/matrix/Split_Loom_Tubing.html

It's time to trade her in for an audiophile upgrade. I don't know what your budget is, but FIM Gold speaker cables look like 2 inch thick snakes.

Here is Richard's (Vantage Audio) "Jackhammer".