Dev, there's no doubt that the Dac1-MK4 was a vast improvement over the MK3. When I got the MK4 I was still using a reference transport from Ensemble, that's still a great piece, however when I auditioned the AA Drive1-MK2 every thing got better(transparency, details, soundstage, extension) but in small increments compared with the Ensemble. So, you might have to let the transport break-in awhile to see if there are significant sonic gains compared with your ARC player used as a transport to make the change.
Also, I don't know what digital cable you are using, but regardless what transport you decide on, I highly recommend you listen to a Stealth Sextet cable. I tried a bunch of highly regarded cables and nothing came close to the Sextet when it came to allowing the Acoustic Arts combo sing to total sonic abilities.
Finally, I use the Ensemble Duo Isolink digital transformer with the the AA combo and it improves all sonic factors by around another 10% to 20% in my system. The rest of my system downstream goes through the Running Springs Jaco power conditioner.
Also, I don't know what digital cable you are using, but regardless what transport you decide on, I highly recommend you listen to a Stealth Sextet cable. I tried a bunch of highly regarded cables and nothing came close to the Sextet when it came to allowing the Acoustic Arts combo sing to total sonic abilities.
Finally, I use the Ensemble Duo Isolink digital transformer with the the AA combo and it improves all sonic factors by around another 10% to 20% in my system. The rest of my system downstream goes through the Running Springs Jaco power conditioner.