According to many respected members on these forums who own REF series DACs (Prickely_Pete, IPodPJ and others), the DSP-1 isn´t really that good at reducing the need for a good transport. The reviews I´ve seen (not many out there though) seem to agree on that - for example check Ravenda´s blogs REF5 review where he compares it to a Wyred4Sound DAC. He also says that the REF5 is still, despite the DSP-1, picky about the transport used.
I just sold my Little Dot CDP_1 transport and currently have a CD7-FV being shipped. With some luck I should have it next week, then I´ll be able to post some concrete impressions on how much a CD transport change can do. From what I´ve read, it should be a very major upgrade, especially when used with Audio-gd ACSS gear as it uses a technology similar to it for the SPDIF output (great synergy, as it has been created to compliment the REF series perfectly).