I own C-1's and have owned Harbeth 7 es III and SHL-5's. I have huge respect for both Harbeth models and have enjoyed both of them, though the metal tweeter in the 7 es at times can be metallic. The midrange, however, is sublime.
As noted by Nolitan, the Harbeths are more forgiving and sound quite good with modest gear and if your objective is to kick back and
listen to music without pushing the envelop, the Harbeth's are an excellent choice. The are indeed very musical and satisfying.
The C-1's are on another level in terms of bass energy, transparency, speed and high frequency sparkle. Like most really excellent speakers, they will take work to get it right, but the rewards can be hypnotic. In a small to medium size room, they can achieve a level of realism that is truly amazing for a speaker of its modest dimensions. If you are willing to invest the time and resources, they are among the elite monitors available.