The two 100w lights should defiantly get you started for seedlings and a few weeks of veg.
Really depends on a budget you have in mind. Lights can vary greatly in price. I think anything in near the 500 watt range would be plenty for that space. One of my favorite for that space is the VIPARSPECTRA KS5000. Amazing coverage for a 4x4 grow tent.
A lot of growers are now going with the multiple bar lights to spread the light out more evenly. Also if you can get a light where the ballast is able to be mounted outside of the tent it will help tremendously with heat.
I hope this helps.