One of the constant criticisms of Seattle Sounders is that they do not play in a Soccer Specific Stadium. Which begs the question, what is a SSS?
For me, it is simply a stadium designed with soccer in mind (hosting about 50% of all sporting events as soccer), with a low crown, with a full size FIFA pitch and a closeness of the fans to the action. Revenue control by the club is important, but obviously not a requirement (here's looking at you TFC).
I don't think size is a requirement. Size is only a test of the marketing and sales teams of the organization. Top Euro stadiums are between 25k and 100k, that doesn't make them any more or less soccer specific, and it shouldn't in the USA.
This coming year we are going to see Qwest host at least 20 soccer matches, and at least 10 NFL matches. So why does most of the North American soccer community refuse to believe that Qwest is as much a soccer facility as it is an American football one?