This may help. I recently auditioned a Boulder 865 integrated amp as well as the Boulder 850 monoblocks with my Wadia 381i CD player (not quite as good as the s7i but a great player nevertheless). I preferred by a slight margin the Wadia direct into the monoblocks as opposed to going through the integrated amp, but both were very good. Now the 850 is a better amp than the 865, but not overwhelmingly so. I thought the Wadia direct was purer, more transparent, perhaps lacking a little of the immediacy that the 865 brought to the table with its preamp. I think the new Wadias are just great minus the preamp, but I also think you can't go wrong using the Wadia with a really good, transparent preamp. The differences are just not that great and you'll get great sound both ways.
Wadia S7i direct to amp
Looking at simplifying my system, wondering if anyone has heard the new Wadia S7i direct into an amp, and if so, how did the pre section fare? My experience w/ an 860x years ago was that the pre wasn't good enough for me to get rid of my pre at the time (a Cary SLP98).