The DWS779 and 780 are identical with the exception of the LED blade positioning system (XPS cross-cut alignment system), which can be added to the 779 for ~$60, with documentation and pictures all over the internet and here on GJ.
This thread is about the 782, but the same parts convert the 779:
https://www.garagejournal.com/forum/showpost.php?p=6457285&postcount=24
Most Lowes will price match Home Depot, so using Lowes (10% off) gift cards should bring the price of the 779 to $360.
Add the ~$60 for the XPS parts, and you have a DWS780 for $420, or less if you get additional discounts from Lowes (like prior military).