EVP is Sprint's "employee value plan", I think. You should check with your company to see if they have a discount with Sprint and if so, how much.
My company has a 12% discount on plans and phones and such.
As for Wirefly, there may be a state that they will charge you sales tax, but I don't know which one would. I didn't pay any sales tax when I got my last phone through them, and 2 people I know that got their Incredibles through Wirefly didn't pay sales tax either.