That is why I gave you a ratio. I would probably do:

• 12 oz. of cream cheese (One and a half 8 oz. bricks unless your store sells 4 oz. bricks.)
  
• two sticks of unsalted butter
  
• 4 oz. of brie
  
• season to taste with salt, white pepper and/or nutmeg (this is what John likes to use)

I think this is a good amount for two people. You'll probably have some leftover, but won't be drowning in it. :)