I guess it really does come down to how much you want to spend. The Arcam is more refined and should be considering price. For under $500 brand new, the Cambridge is hard to beat. For used do not forsake the original D500. It has a slightly older delta-sigma 20bit DAC, but it is actually a higher spec DAC than the 24bit/192 DAC in the D500SE.
I also recommend the power cord upgrade for the Cambridge. The stock cord they give you is pretty cheap. It does not even fit well in the IEC socket. Even a $7 Black 14AWG computer type cord is a good upgrade. I highly recommend the Blue Circle BC61 or the Vansevers 202. The D500 should go well with your Cambridge Amp (which amp?).