Your site: Generated in 1.868 seconds. Look at the generated time. Atahualpa cannot do anything with the speed at which additional and/or external files are loaded, or the speed of the hosting account.
The "Atahualpa slow" posts come up now and then but even a plugin author who dissected the theme quite a bit couldn't say more than that the theme throws a lot of data around under the hood, but he admitted that he cannot complain about the speed.
I improved a few things though, and Atahualpa 3.2.1 is going to be about 0.1 seconds faster than 3.2. Another 0.1 seconds can probably be saved at a later stage but I didn't want to do such a big rewrite right now.
On idle server, 1 plugin installed (Feedsmith),
no Super Cache
no WP Cache, nginx, PHP-fpm, Xcache:
Atahualpa 3.2.1 - 0.300-0.400 seconds (homepage 0.400, page 0.300, single post 0.350)
Default Theme - 0.280 seconds (homepage, but with less widgets because only 1 sidebar)
Test:
http://wpnginx.bytesforall.com/
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On a loaded server (THIS server), Apache, mod_php,
no Super Cache
no WP Cache, 15 plugins installed: This should resemble the average (budget) shared hosting account fairly well.
Default Theme: ~ 1sec.
Atahualpa: 1.3-1.5 (but with more stuff in the sidebars than the default theme = 2 sidebars). First load may take 2 seconds
The server load, and the amount of external files loaded (and the speed of the servers serving the external files) has a much greater impact than Atahualpa vs. Default.
PHP Speedy is another accelerator you can look into, it'll combine external files.