It's my experience that web designers don't always have that much on the ball with databases. Does the website connect to your own stock control DB, or do they utilise some sort of extraction mechanism? And if they are using your DB, is your stock control application slow as well?
It could be that you just need some queries tuned, or a new index or two to get the site humming. Normal links seem fine, so it's unlikely to be the web server hardware that's deficient. Much more likely the database end.
It looks like your website is be located in California, so I do hope it's not connecting to your own DB, or that would certainly cause some latency, not to mention security concerns.
Looking at the source code of a couple of pages, I'm glad I'm not maintaining it. All the inline CSS and inline images in BASE64. Nasty. Possibly something to do with the Magento/PHP platform it was apparently created in.