I'm planing server configuration for my Oxwall project.
As I can see oxwall.org has more than 10 000 registered users. 40 registered users are online along with some unregistered users online.
Due to Alexa response time of oxwall.org is Average (1.443 Seconds), 51% of sites are faster.
As I can see you use only one server for oxwall.org shared with some other projects.
What is your server configuration: RAM, CPU?
What is average number of daily visits?