I checked your site with webpagetest.org :
http://www.webpagetest.org/result/130803_C5_3FE9/1/details/
You are loading a lot of information from a lot of different places– Facebook, Google, Twitter, Pinterest, doublclick… You are loading something like 80 resources from remote locations (To be honest, I lost count but that is in the ballpark). That is more than half– 55-60%– of the resources your page loads.
The only things that W3 Total Cache and APC can help with are the things that load from your server. Those things load pretty quickly, with the exception of some css (looks like) from the “WP Filebase” plugin, which takes about 1.8 seconds to load all by itself, but it does cache so it is better on subsequent page loads.
If you are going to improve page load time you are in for a significant structural overhaul. You need to take a close look at what you need and what you don’t and remove what you don’t. You need to try to improve the efficiency of what you do keep but that is a dozen questions in itself.
This is not a WordPress problem, nor a W3 Total Cache problem, nor an APC problem. You are just doing a lot and are dependent on a lot of third party servers to do it.