For me the biggest surprise has been how important the quality of the source material is. Radio 2 and 3 live broadcasts with a decent aerial/tuner are amazing (and only 13 bit pcm!). Great LPs are quite common and stunning quality. The occasional well recorded and mastered CD can be fantastic. CD recordings of FM and LPs are almost as good as the originals. For me this has become much more significant that swapping hi-fi boxes and wires."