The pro-ject is designed to facilitate the direct connection of an external drive to a usb input, and I think the iFi is as well. not sure about the others I referenced, but you should check. Regarding the difference in sound you heard, there are two other reasons I could think of:
1) It could be that your DAC is not fully immune to jitter or other noise introduced to it from either your streamer or your cd transport. If that were the case, you could hear a difference between the two. Btw, you never mentioned what model your old streamer was - that could be the culprit.
2) When you changed to cd, you listened intently for differences, and could simply be hearing what you were listening for. That’s a classic opportunity for confirmation bias, something we’ve all experienced a time or two. For a more in depth discussion of that, you could check out the thread “The Emperor Has No Clothes” (though full warning, you’ll have to wade thru a lot of discussion of cars!).
Snd regarding synergy with your system, the folks in my camp generally believe that a streamer, properly implemented, does not have a sonic signature of its own. That’s established in the analogue realm, which means somewhere between your DAC and your speakers. Hope that helps.