I have been doing Website AB Multivariate Testing for over 7 years. The consistent result is that small design changes make the biggest difference to improve your ecommerce and lead generation conversion rates. Most of the AB & Multivariate Testing is on landing pages, sales funnels and the ecommerce checkout process. In many cases, I have seen big design changes actual decrease conversion. Therefore, I suggest an optimization plan starting with a limited budget of PPC driving to landing pages, using Google website optimizer. This will help you execute a winning design strategy, plus you will learn which marketing copy to use going forward, plus apply that messaging to banners, text ads and other advertising.
Here is a new landing page design that just went live. This page will be used to test traffic from PPC ads, direct mail and print advertising. Please comment and let me know what you think.