Overall, I much preferred the sound with my preamp in the chain. Not surprising I heard a little more detail, here and there. Nothing mind blowing but there was a few songs where it was like I don't remember hearing that before, or at least I don't remember that being as pronounced.
I found vocal timbre pretty much a wash which speaks pretty good of the 740P. The biggest difference for me was the overall sound was thin and two dimensional sounding. It was if it went from 3D to 2D. The sound stage (specially front to back) collapsed. The 740P gives everything a slight warmth and presence that sounds like live music to me, and I found this gone with the DAC direct. It just sounded like a fine recording vs being able to visualize I'm in a live event. Dynamics and Bass were better with the preamp, but I'll give a slight advantage on speed to the DAC direct.
When I consider the MSRP of the 740P is almost double the DAC, obviously the DAC direct is WAY better value. But, in this crazy hobby where we pay crazy amounts for such small changes, I greatly enjoy and am happy to pay for what my preamp brings to my system's enjoyment; even when I'm only using one single input of the preamp :)
I used to own a 600i (v1) and I loved it. It wasn't until I added the 740P before I thought I really took a big step up from it. I imagine the 700v2 must sound pretty nice...