UpViral looks very similar to Kickofflabs. Just to be clear, is the following your idea?
Step 1: Set up a contest on UpViral
Step 2: The participants accumulate points based on your contest rules (send people to your community with their unique referral links?)
Step 3: People with the highest score get the contest and you reward them
One caveat here is that the community members don't have their unique referral link to send others to sign up for the community.
I might have misunderstood your idea. If that's the case, please feel free to correct me and possibly add additional details.