Hello,
I took a quick look at your site and your speed issues are centering around the generation of the page, while the server does take some time to send the files to the client. The main issue centers around MODX and/or how php is configured on your server.
The others are correct in that you want to cache everything, especially Wayfinder. getCache can help with getResources, and general caching of everything else in general.
Frogabog's suggestion is another good one, as all the javascript needs to load before the page will render if I recall correctly. Granted it's not going to cause 19 seconds of delay in loading the main page, which is your issue.
If you can tell us some about how your server is configured to interact with php that would be helpful, in addition to caching everything. You can also try switching out more complex uses of output filters for cached "if" calls, which should help more as well.
You can use
http://tools.pingdom.com/fpt/ to test where things are being delayed, to a degree.