I had similar dillema to Yours. I have Berkeley Alpha DAC with digital volume control to my active Backes&Muller speakers and think dont need a preamp. In the manual of Berkeley they said: If You dont want loss fidelity dont use a pre.
I tried some budget pre and overall sound was worst.
Next I tried better preamps of my friends in my system ( Mark Levinson no26, Sonic Frontiers SFL-2) and I like it more.
Finally I bought tube Joule Electra LA-150mkII and couldnt be happier, now sound is more palpable, rich and colorfull with ubeliveble weight.
So summary, If You want preamp it must be really the good one
I tried some budget pre and overall sound was worst.
Next I tried better preamps of my friends in my system ( Mark Levinson no26, Sonic Frontiers SFL-2) and I like it more.
Finally I bought tube Joule Electra LA-150mkII and couldnt be happier, now sound is more palpable, rich and colorfull with ubeliveble weight.
So summary, If You want preamp it must be really the good one