Streamer for Kii3 speakers

Am currently using a NAD 390 DD integrated amplifier to stream analog to Kii3 speakers. Thinking about an upgrade.

Wonder if anyone can comment on whether the dCS network bridge would be a better upgrade than a NAD 658 preamp.  Or whether either would be upgrades at all.  This question is not as stupid as it appears at first sight.

Issue 1)
The NAD 390 DD is a simple elegant solution, and does not use a conventional DAC  - as I understood, the up sampled stream after applying a low pass filter is sent out directly as an analog signal.   The unit is also tweaked to hell...... and beyond!  CS2 footers, red hft's, giron shielding for all internal components and transformers. 

The 658 uses a conventional DAC, where the signal is converted to analog by a separate internal DAC.  BUT... It offers a good quality room correction.  NAD Electronics are of the opinion that the two different systems are a matter of personal taste, but the Dirac room correction tips the balance towards the 658.  

But the room is treated, and Kii's are already set to maximise their own room correction.    So am not sure this would be an upgrade at all. 

Issue 2)
The dCS network bridge is already well constructed.  So I think that tweaks would not be that effective.  Its intrinsic quality is already brilliantly thought out and executed.  But would it be better than the tweaked NAD?

I have tested both analog and digital connections from the same source to the Kii's, and cannot tell the difference, so please disregard that aspect. 

Grateful to hear your thoughts....

Best wishes