Does it really matter to whom the order is given up! Unless you are a professional, hedge fund, pension fund or bank there's little the suppliers identity will afect your trading.

It does give a vote of confidence however any broker which has decent volume and may manage the collateral will utilize a PB. E.g. rabobbank enables u to get set up for as little as 500k collateral - but they do have many restrictions esepcially for holding weekend positions