The HD2500 is a 3rd generation graphics technology and The Maximum Display Resolution it supports is 2560*1600.
The link below shows the information about your graphics controller technology. 3rd Gen HD Graphics Quick Reference Guide | Intel® Developer Zone
This article will provide some FAQ related to multiple displays http://www.intel.com/support/graphics/sb/cs-031040.htm
YES, it supports 2560 x 1440 and looks great on the 27" monitor!
You MUST use a Display Port to Display Port cable. With a Display Port to HDMI cable you only get 1080x1920 max resolution.
I thought this would be helpful for others, for HP and Intel could not confirm that it will work.
FYI, I have an HP Elite 8300 SFF with the intel HD 2500 graphics chip-set and it works perfect at 2560x1440.