Is My McIntosh C52 Pre-amp The Weak Link?

@soix  is correct.

@jastralfu makes a very good point

I would suggest having a stand-alone DAC also. You're just swaping out your issue (The C52 having a built in DAC) with a new issue (having the DAC built into the Streamer). 

I am not a big fan of seperates either (I own an integrated amp), but have found disappointment everytime I had a DAC built into another component. I own a N20 by the way, with a PS audio DAC (version 1).

I would also suggest listening to several DAC's, I have found they all sound different.

IMHO, keep the Mac, but upgrade the DAC.

Another vote for getting an external DAC. If you like the Mac keep it. I personally am not a fan of McIntosh preamps but that is just me as I know many people love them.

I have paired an MSB dac with McIntosh gear and to my ears it sounds good.

Get a proper DAC, but maybe one with a good digital volume control you could get rid of your pre as well.

Once I got my first DAC with a built-in volume control (exasound) I sold my Mcintosh c-38, as the DAC was more neutral. It took a while to get used to it, but once I decided I didn't like the colouring of what the pre did in my system there was no going back. I believe the volume control in my Weiss DAC is better than the exasound was. It has a decent streamer as well.