Vincent, all things being equal (whatever that is!), the Wired4Sound DAC has volume controls and can connect directly to your amp without a preamp . . . in fact, that is the way it supposedly sounds best. I have not tried it yet as I am in the process of reconfiguring my system, have a couple of things out for repair, and need to first get things positioned right to try it.
In the meantime, it seems the issue is how the DAC in the Transporter compares to an outboard DAC and whether there are any other differences the Transporter offers over the Squeezebox and an outboard DAC.
In the meantime, it seems the issue is how the DAC in the Transporter compares to an outboard DAC and whether there are any other differences the Transporter offers over the Squeezebox and an outboard DAC.