I do wish you success.
I can't speak for others, but I wouldn't mind you expressing you opinions about cables. However, it would be helpful if you would include something like "Owner of blacksandcable.com." or "President and CEO of blacksandcables.com." prominently in your signature. Just because you have a bias (and who doesn't) doesn't mean you should be prohibited from expressing your opinions. What's important is that your connection to the business be plainly displayed so others can take that fact into consideration when reading what you have to say.
Also I would recommend avoiding hyping your business (Axiom does sell cables), and knocking other similar businesses. But your opinions on cables in general would be welcome. Again, just my .02. Others may feel differently.
