Even though my kit was more-or-less complete, it still felt like something was missing; and I don't like that. While making photo's in dark places it always bothered me that I had to use LED based flashlights to light up stuff, which gives horrible color casting. I wanted something better, and so I decided to get a flashgun.
A bit of searching and reading reviews later I ran across a "Strobist" beginner set for a nice price. "Strobist" basically means that the flash is not mounted on the camera itself, but is handheld or on a light stand. The kit includes a Yongnuo YN460-II flashgun and a Cactus v4 wireless flash trigger.The wireless flash trigger allows you to put the flash up to 100m from the camera, and it still fires on the exact moment that it needs to; really cool. 
All in all it looks like a pretty decent kit, and the flashgun sure is bright enough! The cool (or bad) part is that I have to learn how to make photo's with a flashgun now, which seems like a fun challenge. I've seen some real nice photos that were made with off-camera flashguns, and I can't wait to make some of my own. 