Your site's speed was not super fast but within reason for the first page load. The subsequent page loads were quite fast. The first page load may become faster if you go through all 20+ theme option pages and click "Save Changes" on each page.
Plus you could install a caching plugin such as WP Super Cache or WP Cache 2
If you're still not satisfied with the speed, you could install PHP Speedy http://aciddrop.com/php-speedy/
The last option would be to move to another host. The speed of the web hosting account can have the greatest impact on speed, and can easily outweigh all other factors combined.
Atahualpa adds only little to the page rendering time compared to the "Default theme". Certainly not in the 5 sec. range. More around 0.1 - 0.2 seconds.