Sales and Marketing are such broad topics that you will not be able to find  good Sales and Marketing Speakers that can cover the whole range of possibilities.  Instead, you should begin with the take away that you want from the sales and marketing speech and find a Sales and Marketing Speaker that can deliver on that outcome.

For example, I am excellent at sales and marketing via the web.  My specialty is building lead generation engines and using SEO and Social Media tools to drive leads into the engine.  I can teach people how to do this, if fresh, targeted and exclusive leads are a benefit to the audience.

However, if you are looking for Sales and Marketing Speakers that can talk about traditional PR or print advertising, I would be a less than ideal choice.

Ultimately, a speaker needs to know what their best and highest value is and stick to it, even though they customize the presentation to each event and audience.