Older MacPre w/external DAC vs newer Mac pre w/internal Dac

Hi everyone,

Please understand that I have read all the discussions I could find on this topic, but nothing really talked about my issue, which is whether sound quality is better using a newer Mac preamp (c2600) with an internal DAC or an older Mac preamp (c2300) with my NAD C658 as my DAC.  I don’t care about obsolescence of the DAC as I’m happy with 24/192 level.  I am only trying to figure out whether I’ll get better sound quality from a Mac C2600 without my C658, or with a Mac C2300 using my C658 as my DAC.
I have never owned any Mac equipment, so it’s my first foray into the Mac world.  I can’t preview this since no dealer near me has a C2600 and C2300 set up.  I’m buying used, so I know I can resell and reconfigure.  I’m just trying to do the best out of the gate.  I would prefer the C2600 over the C52 if that is your thought just because I like the idea of tubes (I’ve never owned any tube equipment, it’s just the romantic in me, lol).but, if a good argument can be made for the C52 in my situation, don’t let me discourage you from making it. 

In case you’r wondering, or it helps, I have a great pair of Infinity Kappa 8 speakers being driven by 2 vintage 250 watt mono blocks (Cambridge Audio A250’s) and pretty much only listen to digital sources (ripped cd’s, and Tidal) so turntable issues are not important to me and I don’t need lots of inputs.  
My thought is the sound quality would be better using the C2600 because it’s DAC is designed to work together with the C2600 as compared to mixing components.  I have had no problems with the C658 but worry that adding an extra component in the chain would degrade performance. I’m currently using a Marantz AV7705 HT pre with the C658, which sounds nice.  I’m just looking to improve what I have. The system will be a separate stereo set up.
What do you think? (Remember I don’t care about obsolescence of the external DAC, only sound quality)

Thanks in advance,