Ah a VPS does change things. WPSC is great for shared. W3TC is better on a VPS.
W3TC is inactive right now so it's hard to really tell without actually logging in and testing myself, but you have a pretty high server load so that's going to slow you down.
I suggest the following:
1) Remove some plugins. buddypress-post-ratings and wanguard are both good plugins, but they may be slowing you down a little.
2) Optimize your VPS. Go to https://panel.dreamhost.com/index.cgi?tree=vserver.settings& and do the following:
* Turn on PHP cache
* turn OFF Jabber
3) Consider Google Pagespeed. If you go to https://panel.dreamhost.com/index.cgi?tree=domain.manage& and click on edit for your domain, you can change PHP settings there. I would try (and please understand this may not work perfectly) checking the box for "Page Speed Optimization?"
4) Consider PHP 5.4 - Many people reported a 15% speedup on their sites. Same page as page speed, just change the drop down to PHP 5.4 FastCGI