The PCI-6703 itself is not expandable, meaning you can't add extra components to the board to get more outputs. However, you can use more than one PCI-6703 in the same computer if you need more channels. You might also consider using PXI analog output modules. The advantage of PXI is that you can share timing across several modules and can have all your modules in an external chassis. Using NI's new PXI-6608 module, you can even sync several chassis using GPS receivers.