Dreamhost offers both PHP XCache and Page Speed. The XCache works nice with W3 Total Cache. I just had to disable Page Speed because of extensive connections made to my site by Dreamhost servers. I literally had 130,000+ access attempts. DH support actually told me to disable Page Speed on my domains because it doesn’t offer any benefits.
Truth be told, I’ve very disappointed in both the VPS and DS solutions. First off, unless you move your MySQL databases to a private VPS/DS, you’ll be using shared hosting. That just kills the performance. They pack so many users (or resource usage) into a single shared machine that it kills performance.
Without properly configured Wordpress caching with a MySQL VPS (so now you need at least two VPSs), you’re site will be slow as hell. Just a heads up.