The straight answer to your question is that via Bitcoin-Brokers.org you will pay Bitstamp price +12%.  From the help ticket I submitted to Bitcoin Brokers:

Here is your quote and instructions for purchasing these bitcoins.

Transaction ID (sample)
This seller sells BTC for Bitstamp +10%
Bitcoin-Brokers fee on this transaction is 2%
The exact total of your order is $ (sample)

In my case, I wanted 3 BTC so at a current Bitstamp price of $589.46 my price to purchase would be $589.46 + 10% + 2% = $589.46 + $58.95 + $11.79 = $660.20.  For 3 BTC the total comes to $1980.60.  That's a hefty 12% convenience fee of $212.22, and way too steep IMHO. A 2% markup is acceptable, as I was lead to believe reading on this thread and another thread on Bitcoin Talk forum.

You will NOT be able to procure BTC via Bitcoin-Brokers.org for Bitstamp price + 2%.  For 7 BTC you will pay $4621, which will be a whopping $495 above market price after the fees are paid.