Does the Transport make a significant difference

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.

wow some great replies above. my opinion...for what it's worth...is I'd step up the entire digital front end...maybe a used dCS Puccinni...has a pretty good volume control built in. Then down the road a preamp.

I do like a preamp vs digital volume control...but again...in a priority I'd do something like a used dCS Puccini first...get the source as best as you can first.

Since it apears you play CD's, I also would try the PS Audio transport and use the is2 connection, as Stevechamp suggested. I purchased one for under $1500, and am happy using it with a Yamamoto dac( thanks charles1dad)

I have not tried computer audio, but if it's something you are eager to get into, it seems now would be the time.

11-21-14: Ricred1
What are the thoughts on removing the preamp and connecting the DAC straight to the amp?

As Charles and Rja indicated, this is best determined by trying it both ways. And before reaching any conclusions, you should preferably try both the balanced and the unbalanced connections which are supported by each of the three components.

FWIW, though, after looking at the specs and descriptions of the PW DAC II and your Parasound A-21 power amp, and measurements of your Aerial 7T speakers (the sensitivity of which will affect what part of the range of the volume control that is used), in this particular case I see no technical reason for a preamp to be necessary. Whether or not it would be subjectively preferable to include one is another question, of course.

FWIW, my own instinct in cases of doubt is to keep the signal path as simple as possible, by not including in it anything that has no clear basis to be included. And if that turns out to be the alternative that is less preferable from a subjective standpoint, to try to determine the reason, and to correct the issue by changing a component rather than by adding a component.

Good luck, however you decide to proceed. Regards,
-- Al