Mcintosh C49 C55 C2700 C2800

Right now my set up is C49 Pre amp, MC352 Amp and Cornwall IVs. The C49 has the DAC1. Is the DAC2 worth the upgrade?

Well I have heard all the last gen (49,2700 and 53). In isolation they are all 100% fine and you probably could not guess which one you were using. I personally hate replacing tubes and would go with the C53. 
 

If you are all digital the MDA200 has the same output stage and DAC as the C53 and probably sounds the same… food for thought. It is $4000

Referee1, Any impedance matching concern using the tube pre with solid state monos? Assume you are using the balanced amp inputs (lower impedance)

That sounds like a nice combination. 

I've been using the c49 to drive my MC611's and do consider stepping up to the c2700 or c53 for the tone controls, but the kit is so good as is I struggle to get motivated to change anything! 

@referee1 

I have a C2700 feeding a pair of MC 611s—a great preamp with outstanding functionality. Also, the DA2 module is outstanding; it will compete with anything up to $5K. I know this because my separate DAC retails for $19K and does everything better, but the DA2 puts a smile on my face for its value. The DA2 module is also modular, and I have a feeling that in a couple of years, a DA3 is on the horizon. 

found this today. 

Brother Vs Brother: McIntosh C55 Solid State Pre Amp vs C2800 Tube Pre Amp (youtube.com)

I have had a C2700 for some time now and can't say enough good about it, very flexible preamp, probably one of the most flexible out there. The new C2800 adds some remote app features that I'm not overly concerned about for my use. I bet you can get a C2700 for a good deal now that the C2800 is out. If you don't care for tubes then the C55 will fit the bill as well. I don't think the 49 comes with the DAC 2 board.