I was originally only going to breed one mare this year, but am now thinking of breeding my homebred mare Forte (Freestyle/Wolkenstein II/Arkansas) again. I need a stallion that is GOV approved and prefer to use frozen semen due to the CEM thing. I am breeding for an upper level dressage horse, doesn't necessarily need to have a dead quiet attitude for an amateur.
Things I need the stallion to improve: Correctness of front legs and need a longer, higher set neck. The stallion should add some height or at least not take away from it.
The mare is already a phenomenal mover with an excellent hind leg and lots of elasticity. I wouldn't mind adding a bit more knee action to her movement.
She excellent trainability/rideability, sensitive in a good way, but it very much a worrier in her stall and gets very stressed out when going to new places. I don't mind a stallion that produces "hotter" riding horses, but need a stallion that produces more mellow temperament around the barn, if such a thing exists.
For length of leg and more knee action, I always immediately think of Sandro Hit and sons such as Sir Donnerhall, etc., but they may not give you the quiet, mellow temperament you want. The Sandro line tends to be somewhat sensitive and easily stimulated, and I have heard of more than a few Donnerhall line horses that don't handle travel very well (stall walkers, diggers, etc.). This last is somewhat surprising how successful and popular his offspring have been with professionals and amateurs alike, so I certainly wouldn't rule out one from this line.
I would shoot emails to Katrin Burger and Holly Simensen and see what they recommend. Also check with some of the semen importers who travel regularly to Germany and are familiar with the stallions there.
If she were mine I would breed her to Sir Donnerhall. My Sir D x Rosentau/Arkansas is turning out to be a superstar and the movement is pretty WOW. Honestly. He will reliably put on lonnnnggg legs and usually that round topline as well as a beautiful canter and suspension gallore. Mine was shy at birth but came around really well. She is sensitive and hot but still sensible. So if mine is any representation of her sire, I wouldn't hesistate. I would just make sure your mare is textbook behind and has a good walk.