Only a person who works with WordPress a lot would recognize the theme used for David Carron’s web site, and even they might have to peek at the source code to identify it.
David’s site is built using a child theme based on the default WordPress theme Twenty Twelve. The main menu has been moved, the tag line is in a new location, there is a custom logo replacing the site title, and a slider has been added to replace the default header image. There have also been a number of changes to the default colors, the default fonts, and other CSS tweaks.
The workaround I suggested was to start with a default WordPress theme, create a child theme based on it, and to modify the child theme so that it matched the simple, professional look they were going for.
I’m a firm believer in working from a child theme; doing so allows the developer a lot of freedom to modify the look but prevents updates to the parent theme from overwriting the modifications. It also makes it possible to use one of the default themes supplied with WordPress, which is one of the best ways to avoid coding conflicts and problems down the line as long as all modifications are done in accordance with WordPress’ best-practices for coding.