A signdesigner designing a website is the same thing as a webdesigner designing a sign...sure they can both do it, but it usually shows.
SEO is another story, anyone can study up if they have, or make enough time. Implementing it into your site effectively and maintaining it is another story.
The hardest part is to create a site that is both visually pleasing and ranks really, really well... everything is a compromise. You change and tweak chasing rank until your site may end up looking nothing like you had intended.
This is where someone like Dan excels...he can take your vision or ideas, implement an SEO strategy from scratch, design a beautiful site, make it rank and make it pay.
I've looked through thousands of sign related websites and 98% of them are hopelessly SEO under optimised.
Go to alexa.com and check the rank of your site...what's yours? How can you improve it?
How many hits a day are you getting?
What's your bounce rate? How can you improve it?
What's the most popular pages and exit pages?
What keywords/phrases are driving traffic?
Are people landing on the pages you want? Are they exiting through the 'contact us' page? If not, why?
How many pages are people viewing, how do they navigate through your site?
How many enquiries and phone calls are you getting per day via your site?
These are the questions you should be asking yourself.
A nice site is just that...a nice site.
A great site is one that makes you money.
just my thoughts...