restrict saving a record in a particular sales stage to only 2 users

Hi,

We are trying to restrict people from saving an Opportunity in a 'Closed/Won' sales stage.  We would like to grant this privilege to only 2 people.  Right now, I have the following workflow in place that will only allow one person to make this save, and for everyone else, it reverses the sales stage back to the previous stage. 

Before modified record is saved.  Workflow condition:

(PRE('<SalesStage>') <> [<SalesStage>] AND FieldValue('<SalesStage>') = "Closed/Won") AND (UserValue('<EMailAddr>') <> 'xxx@xxx.com')

Action:

Change Sales Stage to 'Tie-It-Up'

Two questions:

1. How can we add another user to this workflow?  Any way I try to add another email to the equation, the workflow breaks and won't allow anyone to save in 'Closed/Won'.