Benchmark DAC1USB vs PRE1 vs Transporter

Since the Transporter has no usb in I'm guessing you mean ethernet in, or add an USB to SPDIF converter.

For the price of a Transporter you could get a Squeezebox Duet and Dac1 Pre combo.
That would give you cheap multiroom expansion capability and a handheld GUI rf remote. You would have both a digital remote volume and Dac1's analog volume. Set the Dac1 at close to the listening sweet spot and do minor digital volume adjustment remotely. When feeling purist do so manually.

Can you get the Duet w/o it's dac or not? I love the duet function but if you have a benchmark why do you need another dac?

I was in the same boat. I went with the Transporter. I already had a Squeezebox thus I didn't need the Transporter for the wireless capability. After doing a lot of reading, I decided the Transporter would sound better as well as limiting the number of pieces on the rack. It's close to my Rega Planet CD player.
Here's a couple of URLs you might find interesting.

http://www.slimdevices.com/temp/noise_floor.gif
and
http://www.slimdevices.com/temp/transporter_vs_benchmark.gif

Saunderse wrote: "Forget the transport with the volume control. I guarantee you, that the pot in the transport, is in the signal path and is probably of very poor quality."

This is incorrect, both the SB3 and Transporter use digital voume control; see:
http://forums.slimdevices.com/showthread.php?t=39611&highlight=digital+volume+control