I have a Pass Labs 250.8. As some others here have said, the ARC REF6 has a very sweet synergy with the Pass. I also tried going MSB DAC to amp, and VAC Renaissance Mark V as well, and the ARC REF6 sounded significantly better to me. Replacing the stock power cord with a Shunyata Alpha v2 really kicked it up another notch as well. I have heard good things about Backert, but not having heard one in my system, can't say. I can say that you won't be sorry with the ARC Ref6 (but nothing lower . . . I first tried an ARC LS28SE and was unimpressed. Just a little better than the MSB direct to amp). ARC preamps really hold their value as well.