snakeeyes
The answer is both yes and no. I suppose yes they would tip easier than speared directly to the carpet. But, realistically, no because they are so dang heavy and stable. They are not top heavy in the least.
I have seen tall, thin, and easily tipped towers. The Salks are not an example of an easily tipped or moved speaker. And add to that its just me and the Mrs. and the Mrs. doesn't venture in to the audio emporium very often. Without a tipping agent, gravity and the laws of bodies at rest rule the day.
If you go to mapleshade.com you can find excellent examples costing $100's of dollars to place your speakers and equipment on. All with fantastic claims of audio wonderfulness. Or, do what I did and go to Ikea and spend $8 on two bamboo cutting boards and you're done. This was just stuff I had laying around and its strictly for looks. No claims about anything.