Also wanted to post my findings on comparing the Accuphase E-380 used as a pre-amp vs using a Holo Audio Serene pre-amp.
I am using relatively inexpensive RCA's to connect my E-380 the S5.5. They are good but not at the same level as the rest of my cabling, but I bought them to test the Accuphase as a pre-amp with the understanding that I would either sell the Accupphase and get dedicated pre-amp and connect via XLR or I would purchase a higher end set of RCA's if I wanted to keep the Accuphase.
My friend brought over his Serene and we fist listened to the Accuphase and then listened to the Serene using the same RCA's. We found the Serene to be a very good fit with the S5.5 as is the Accuphase. They both sounded very similar but there were 2 main differences.
1. Using the Serene the bass was quite a bit better. Faster and more of it.
2. Using the Accuphase the upper range frequencies had more sparkle and sounded a bit better.
I would be happy with either and they both seemed to fit really well with the S5.5. Then we swapped out the XLR connection on his Serene. Once we did that there was a huge difference in overall sound quality, clarity, bass, etc. Everything just got a lot better. It is worth noting that the RCA's I am using are around $100 where the XLR's we tested are around $2,000. So, how much of the difference is in the XLR connection vs RCA and how much is due to the cable? That is the big question. I tend to think about 80%+ is due to the quality of cable but I am not sure.
I did just borrow a pair of Nordost Heimdall 2 RCA cables from my local hi-fi dealer and will test this weekend with a higher quality pair of RCAs.
I do not know enough to know if RCA or XLR connection from the pre-amp will yield better sound, but will find out in a little while if a nicer pair of RCA's enhances the sound.