Mm, I looked at the optimization page you linked and I've already gone through most of that except the .htaccess stuff, which I'm not comfortable with editing. If the cache plugin in supposed to HELP page speed, then the only other plugins I can think of that could be a problem are WordPress SEO, SEO Friendly Images, and/or Better WP Security. Those and the cache plugin are the last four I installed/activated. Before them, my site was fine - so I don't believe it's the theme or anything like that.
Has anyone else had any problems with slow loading times after using one of these plugins?
I may try disabling the SEO stuff. The security plugin I hesitate to deactivate because I really do like the insight it provides...also, it gives me an easy way to ban those IP address you sent me.
Any other advice or suggestions from anyone are welcome. I am really unhappy about my site's performance lately, for the first time in my (almost) 9 years with Dreamhost.