Hi Jose, your site is not too narrow in my opinion. It’s about 920px wide. If it looks small on your screen it is because you have a very high screen resolution.
47% of internet users (Sept’ 08) have a screen resolution of 1024 x 768 so your site is almost full screen for half your visitors.
You could make your site Auto width but this would involve a lot of modification.
I also see there is an option to have a wide or narrow option on this template. It is possible that you viewed your site in narrow view and then set the template to wide but your cache still has your view set to narrow. Clear your internet cache to solve this.