The home page is about 1.1MB in size, and from our tests you're running less than 5 seconds. When I ran through
http://tools.pingdom.com
There's connections out to facebook that could be causing some of the slowdown - can you try temporarily disabling those modules?
The "feat_children.png" image is also not loading. As a result, it'll slow down the site as it continues to try to load (
http://www.star500.com/shop/skin/electronics_black/images/feat_children.png)
If you could combine some of your regular images like your forward/back arrows and lines and make them into a sprite - that would speed up things too. Also, pulling some of the data from a separate subdomain would help too. You could easily setup "template.star500.com" as a subdomain, point it to your template folder and have some of your more common template parts of X-Cart pull from that subdomain. A browser can pull data from 5 different domains(subdomains) at a time, but only pull 2 items of data per domain - that means it has to wait on "A & B" to deliver before sending "C". If you were using even ONE extra subdomain, you'd be delivering "A & B" and "C & D" at the same time.
Personally, it loaded fast for me, so it might have been a server load issue too.