Matching streamer/DAC combination to SQ of my system.

My question may be unanswerable in a meaningful way. I guess what I'm asking is: what would you (who are more experienced than I am) plan to do in my shoes?

I have a nice older amp--a Musical Fidelity A308, once the flagship of their line--and ATC SCM 40 v2 speakers. The weak links in my system are a relatively low-end DAC and the fact that I stream from a Mac. Generally, I don't have a partIcularly warm sound in a complex listening room.

So if I wanted to buy a streamer/dac unit, what price range would do my amp and speakers justice? What would represent overkill, or not enough improvement to be worth upgrading? For that matter, what specific units would anyone recommend? My budget is limited by my common sense, not my bank account.