Technical Question - Tube Preamp

My sources are mac mini music server and Oppo BDP-95 into my Bryston DAC which then feeds my Anthem 225 Integrated Amp.

I recently acquired a Classe-S700 Amp and use my Anthem as a preamp. The plan is to replace the Anthem with a tube preamp.

The question is " Am I doing the right thing of replacing the Anthem with a tube preamp and also do I need a Bryston DAC in this mix if all my sources go into the tube preamp"

Most of my music is computer - so mac mini will be a primary source.

Thanks for your inputs.

Get a tube preamp it will improve your sound.

You will need some kind of DAC.  Although not common there are a few tube pre-amps w on-board DAC, including Monarchy M24, Jolida (several) and Peachtree Nova.  There are undoubtedly others, or you could go w a separate tube pre-amp and DAC.   
You do need the DAC in your planned configuration, since you already own the Bryston, assuming you like it, you're all set, just add a tubed preamp as you are intending.
If you want a tube preamp get it ,you already have it all.
I have used a Mac Mini into a Bryston BDA-1 DAC with a Jolida tube pre and now a Aric Audio tube pre. I believe using a tube pre will benefit your system. Improvements in soundstage width and depth, immage specificity, and timbre.
Hope after four years the OP has found something!
limoangus hasn't caught on yet.