I've owned both the D300 and the D400 Mk 2. I would really recommend going with the D400Mk2, this is probably one of ARC's best amps. Much better bass control and transparency. My D300 also ran smoking hot(ran it bridged for a while on a centerchannel with my D400 for left/right) compare to just hot of the D400. The only problem with the D400 is it is a huge amp versus the typical sized D300.
I used both amps with an Audible Illusions L1 preamp so your synergy will work better there. funny I also used MIT 330/750 cables back then too but with Magnepan IIIa's.
I used both amps with an Audible Illusions L1 preamp so your synergy will work better there. funny I also used MIT 330/750 cables back then too but with Magnepan IIIa's.