Choosing a Linux server distribution

Two large monolithic projects launched many years ago required new capacities from both hardware and us developers. In this regard, tomorrow a new HP server will be put on the rack on which one of the projects will be transferred. Raid 5, 4 cores and some other pleasant things that do not require mention. Rise will exclusively Linux environment. From which the question arose about changing the current Alt to something more adequate and responsive.

Average:

• 200+ requests per minute.
• 80,000 visitors per month (according to Analytics)

The java project and related requests for software and its adequate work:

• apache 2.2
• jre6 *
• jboss4 *
• postgre 8
• AOT (search)
• + monitoring services (hardware, web-server, etc.)
• + convenient remot control

The load of the project is constantly growing and at the moment is limited only by the performance of the server and software on it.
The choice of a distribution kit is of course only one of the issues to be solved, but very important for a start.

I ask the community to participate and help determine the choice.