Some monitors allow multiple inputs and have a special mode which allows them to display both outputs together, side by side. !DualHead now makes use of this to give you a higher resolution screen than should be possible with the Titianium.
You will need the right sort of monitor (R-Comp will be happy to sell you one if needed), and you then plug in both monitor outputs from your Titanium. You are still limited to 2048x2048 output on a single screen but using this trick you can get around this issue. The configuration software gives you easy access to these 'new' modes in the bottom half of the drop down list. So you can now have 2560x1440 or higher resolution modes from the Titanium.
I look forward to seeing what R-Comp have planned for release 4.
R-Comp website