Dear Adrian,
I am not sure if you are still interested in the transporter, but I have just bought one and am very thrilled with it. I used to run my Squeezebox into my DCS dac and upsampler, but using the transporter as source has improved matters immensely. I once had a very fine CD-drive (Audiomeca Mephisto), but I guess the transporter trumps it. The clock link is an improvement, but then you have to use a Dac that allows operation in master mode outputting a clock signal. That narrows down your choice. Only DCS (buy used!) and Esoteric come to mind.
Best
René