4
top 16 for each round qualify for an end of year slugfest (TOC)
only issue: once you make the top 16 your out to make room for others
If there's going to be a TOC, I think you'll have to determine participants by a "points" system. Something like 1 point for Round #1 win, 2 points for Round #2 win, etc.
Just allowing the top 16 for each tournament invites could lead to problems with a TOC bracket (maybe there'd be 17 people, etc.) With a points system, you can invite the top 4, 8, 16, whatever scorers to the TOC. If there are people tied for the last slot, have a mini-competition of some sort to determine who gets the last slot.