I just answered you on your other thread since I saw it first but here is what I said:
I've never sewn on the Horizen but I did purchase a Serenade a couple weeks ago. I LOVE IT! I've been sewing on a Pfaff 7570 and it is like my Pfaff on steroids! BTW, the Serenade has an 8 5/8" harp. Lots of room.