Does the Transport make a significant difference

I find playing the CD disc with a good transport gives superior sound to the same CD ripped to a PC and played back with Jriver. I know other enthusiasts who experience the same result.

If you have that DAC you owe it to yourself to get their PWT and connect them via the I2S ports. I guarantee this will be the best CD you have heard. I have a PWT and a Wyred 4 Sound DAC 2 SE with that same connector it sounds very good.

This is variable, some systems sound better with pre while others do better without. Only one way to find out.

I'm currently running DAC direct into amp.

Agree with Rja, active preamp vs direct DAC just try both methods in your system and compare. That topic has been discussed it seems a thousand times on audiogon. The answers never change.