adding DIP to mega changer, any difference?

Sean's correct. The DIP made more improvement in my setup than the external DAC !! This suggests the weakest link of cheap transports is signal jitter rather than DACs or analogue outputs. My setup:
Mission PCM 7000->DIP->Monarchy 22A. This setup cost me $400 and kills my old Marantz CD67SE.

I have a DIP on my Sony 555ES. I concur with others that the addition of the DIP was as significant as the addition of the DAC. I will add that digital cables play a big role also. Expect to spend $500-1000 for the digital cables connecting CDP -> DIP -> DAC.

Well, my two digital cables cost a combined $50 because they're home made. I used RG217 mil spec low loss coax, and I have put a ferrite clamp on the cable from the transport to the DIP to try to reduce noise from the transport from interfering with the DIP / DAC.

I concur that digital cables make a surprising difference, but I am not convinced that you have to spend a lot of money. Similarly with analogue interconnects. Twl recently posted an analogue interconnect recipe that costs approximately $1 per interconnect (plus the cost of the RCAs that you choose). And they sound amazing ... better than $200 commercial cables. I sound like a 10 10 220 commercial .. an interconnect for a buck !

Homebrew ... it's the way to go.