VIdeo on Nikon DSLR?

I was wondering if I should buy an ATOMOS for HD Video on my DSLR. I have reviewed footage straight from the camera and I could call it satisfactory, but I know the ATOMOS would produce much better video. But that would also mean buying a solid state hard drive along with a slew of other accessories, which would be rather costly.Also, thank you for help.

Save your money and get the right tool for video: A camcorder which will cost you far less and produce better videos with much fewer instances where you have to restart because of using a DSLR.

"I know the ATOMOS would produce much better video."
The ATOMOS doesn't produce video.

It might allow you to review and edit the video better than the built-in monitor on the camera, but your camera is still responsible for actually creating the video. If your camera doesn't capture HD video, this tool will not help.

Your first purchase after the camera should definitely be lighting, even if it is just a single fill. Getting a field monitor at this point will merely show you how poor your current video is if it was shot in bad light.