It really depends on how much it costs (does it matter to you?), do you want to stop somewhere along the way, do you mind how many connections, do you have to stay within an alliance?
You now mention buying Prem Eco and then upgrading which also limits your options.
The quickest and all lay flat option is United. Brussels to Newark and then non stop to HNL. It is far from the best business product out there but the seat is comfortable, the food acceptable and the service..... well that is always hit or miss.