|"what are the D-Sub + DVI and HDMI on board for?"|
The board itself does NOT have an integrated graphics chip. The graphics are integrated into the CPU. I'm not an Intel fan so I don't know if it's possible to run dual monitors off the integrated GPU or not.
When choosing a graphics card, make sure to check the specs. If you get an AMD card that supports Eyefinity, you may be able to connect 3 monitors to it. Make sure your power supply is capable of handling the load.
"dont need it for high resolution just enough for 19 to 20 in monitors"
Whatever the native resolution is for your monitor(s), that's the resolution you should be running.