Branding is super important. I would build your site based on a brand name and not your keyword for sure.
HOWEVER...I'd also buy the keyword.com/net/org domain if it's available and I'd probably create a blog on there that will eventually link to your main site. Doing this will get you some additional traffic but also prevent a potential competitor from grabbing an EMD and outranking you in the short term.
Hope that helps.