Really? Where are you seeing this? Is this just what you're seeing in Windows in the display settings? Because that would mean it's only showing resolutions your monitor supports.

I'm looking at that card on Newegg, and I'm pretty sure it'll support that resolution (as I would expect a $350 card to do). This is the card you have, right? That page claims it supports up to 2048x1536 at 85Hz.