The amount of RAM (server memory) does not affect the speed of your website. If your website does not have enough RAM, “out of memory” errors will be logged in the server's error logs, and the visitor to a web page will get a 500 error screen. WordPress needs a maximum of 256MB RAM in extreme configurations, most installs will never come to using one quarter of that. Adding more RAM does not have any effect on how fast your webpage loads.