External Display limited to 1080p after 10.9.2. update
The problem is Mac OS X. It is limited (in software, in the drivers) to a certain pixel colour clock rate for the HDMI port. The hardware in the Mac is more than capable of driving your WQHD monitor at 2560 x 1440 etc., but you can't do it via HDMI as the operating system's interface to it is essentially crippled in software.

It'll work via the DisplayAdapter port, though. The downside is that the single Thunderbolt connection will be taken, and you won't be able to connect to your monitor and other gear at home.