Newbee building a retro sound system from scratch. DCM speakers

I too am an owner of Time Windows (52779,52780). My third pair since 1977! Needless to say, a GREAT speaker! Instead of the McIntosh or Marantz I will recommend something far better (and still vintage): a Yamaha AX-2000 integrated amp (1985). Superb build and sound quality. Currently listed on EBAY for $1400 with free shipping.Check it out! If I didn't already have so much gear I'd buy it myself! 

The 2215b won't have enough power.  "15" is 15 watts.  Get a bigger Marantz, those speakers will appreciate it.

I used to live in Ann Arbor, and had an opportunity once to get some Time Frame TF500s at a good price.  I dithered (I was poor!), and when I made up my mind and went back, they were gone.  Much regretted,  I was always very impressed with DCM back then.  Googling, to my surprise I see they're still in business.  You don't hear much about them these days.

I remember them in the '80's. I liked them a lot, but like twoleftears, I was broke.
Regarding your question, you will need a DAC to translate the digital signal to analog.
May I recommend an Ayre Codex?
You can get them used for $1500 or so.
Also, Schiit Gungnir or Yggy. They are in the same price range.
I like both of these manufacturers because they offer upgrades to their equipment, and since Digital to analog is constantly evolving, I enjoy not being required to buy a new unit because they found a better recipe.
B