Ask HN: Experiences w/ Dreamhost & SEO Plugin Vs. Another Host

I can fake my way through some PHP and Django, but I don't know what's going on when it comes to server administration, and I could use some advice.

I've been on Dreamhost shared hosting for several years now, and have been very happy with them.

But recently I they told me that they are getting out of memory errors on my account. I operate about half a dozen sites, mostly on WordPress, my blog, http://kadavy.net being the most popular and critical. Altogether, I'd say I get about 90k unique pageviews per month for all of my sites.

I looked into WordPress optimization a bit, and while I installed and configured WP Super Cache, I noticed that Dreamhost has banned one of my favorite plug-ins, "All-in-one SEO Pack." I'm still using it and they haven't said anything, but I did notice that the WordPress admin ran more quickly on one of my sites when I disabled this plugin.

Is it time for me to upgrade my hosting plan? Should I go with Dreamhost PS, or some other hosting service? If it costs a bit more each month, fine. I may be naive, but it doesn't seem like I should have to worry so much about optimization at this point.