From July 14th 2015, Microsoft will no longer issue security patches for Server 2003, leaving it open to an ever increasing risk of virus, spyware and malware infection, not to mention a plethora or security holes allowing hackers to gain access to a businesses network (67% of IT security breaches happen with businesses employing less than 100 staff).

Migrating your server operating system from 2003 not only reduces the risk from the aforementioned security threats, but for many businesses it also means migrating away from old, slow, unreliable (and out of warranty) servers.Some of the many benefits of upgrading to a new server and modern server operating operating system go beyond reliability and security, some of the many benefits include:

Virtualization:
Reduce power and cooling consumption
Reduce warranty costs
Reduce and consolidate licencing costs (server 2012 r2 standard allows you to run two virtual servers)
Reduce required rackspace
Reduce noise

Disaster Recovery:
Server Replication, lets you replicate your virtualized servers to another location.  If disaster strikes, your servers will be synchronized within 5 minutes of each other, allowing you to bring up a near real-time clone of the failed server (designed to compliment, not substitute a backup solution).

Performance:
Increased processing power to get the job done quicker
More memory allowing you to run modern and complicated applications
Faster storage allowing applications and files to load more quickly