Preamp. I tried direct with PS Audio, Bricasti M3 (loved the volume control) and a few others. Currently running a Bricasti M1 SII through a Cary SLP-05 and love it. Tried direct and as good as the Bricasti is adding the Cary back into the path added a little soul back into the sound. Might be mental or just really like the Cary but I think the pre is a good addition.
DAC DIRECT IN TO AMPLIFIER OR TO PREAMPLIFIER
For the longest time, I believed that the best preamplifier is no preamplifier. Eliminating a component from the audio chain would yield less distortion & greater purity.
Recently, I have had reason to re-think my logic on the matter - and I am (I think) changing my mind. Better said, assuming that the preamplifier in the component you are using (in my case, a DAC) can produce 95% or greater quality sound compared to the preamplifier component, then no preamplifier is the best option. The 5% represents the (estimated) loss of fidelity in adding another set of interconnects.
That said, most DACs do not have an outstanding preamplifier built in. I think most have average passive attenuators, and the better DACs have active preamplifiers that are very good - but not as good as a quality preamplifier.
What are your thoughts?