It really depends on what the purpose of the horse is. When breeding for a performance horse with the hopes of going to the olympics you have different bloodlines in mind than if you are trying to breed a good quality amatuer dressage horse which will be able to do the upper levels.
When breeding for a performance horse the three main traits that one would be aiming for are movement, athletecism and soundness. Ridability and temperment are nice sidebars but rarely happen by accident. As a result these horses are usually only ridable by experienced professionals, especially as young horses.
When aiming for an amatuer's upper level horse the three main traits are rideablility, soundess and finally movement. Athletecism and temperment are nice sidebars and can come with good line mixing. These horses are bred to be ridable by a large portion of the equine community and are generally more sellable.
In my experience many of the dutch (KWPN) lines will produce horses who fall in the first category. Jazz, Krack C, Ferro, etc all tend to produce very athletic horses who are high strung and have a strong personality. There are some exceptions - many Samber horses end up very ridable, however quite sensitive and so need a very soft touch.
My experiences with studs from other books are as follows:
Weltmeyer (and the Hano W line in general) can produce horses either way. Some of the W lines produce athletic, stubborn and high strung horses which will bite, kick and generally be a**holes. However, some of these W line horses depending on the cross are very sweet, sensitive and usually also quite hot.
Akzent and other A line horses are generally sweet, ridable and nice to be around but tend to have lateral walks and soundness issues.
Grande and other G line horses produce heavier set horses whom are more old style, but are also quite ridable.
Donnerhall is a legend and some ******ed percent of horses at the WEG last year had this line. A very good line for both international horses and very ridable horses.
Rubenstein is another very good line, most of his sons and daughters follow very closely his body type and he has many horses in the GP around the world. Another very good line that has produced some great horses (Relevant and Royal Diamond come to mind).
I am partial to Rubenstein's son Rotspon (the sire of my horse). Rotspon has another son, Rigo, who is in Florida competing at small tour and consistently scoring in the 70% range. I would bet that he will be on the Pan Am team. These horses are however usually quite small (16-16.2hh). I have actually met Rotspon and he is insanely nice. His stall door was wide open, he was tied up and he didn't really seem too concerned about anything in particular, except if you had a sugar cube in your pocket. Not studdy at all (although I'm sure training/experience has something to do with that) and generally a really cool horse to be around.
Londonderry is another Hano line which produces a hot, slightly tempermantal horse. Could be an ammy horse with the correct cross, and the right ammy.
Cor de la Bryere is generally considered a jumping line, but is gaining popularity with correct crossing in the dressage world. My horse is a decendant of this line, his damsire being Come Back II.
Come Back II has sired some horses of note in the dressage world, Calecto V and Come On III, both of which have seen success in CDIs and international competition in very recent years. A great typey horse with lots of prescence, athletecism and good rideability, however semen is not available in NA. There are a few sons in NA of varying straw prices depending fame of the horse.
Bolero is a good line to add type, but can be hot, much line the londondery line.
I personally am not a fan of the Sandro Hit craze going on right now. I find the horses to be disproportionate with no real redeeming qualities, they are not particularily athletic and have an average temparment, but are rideable.
Although I have not personally had experience with the Quattro lines, they are very athletic and impressive. Quattro's progeny include Quando Quando, Quantum Tyme and Quarterline. Grandsons include Quarterman (Quaterback's sire). So obviously an international bloodline which appears to be rideable and judging from some of the inspection results is. I am still out on these horses however would jump at the chance to ride one.
Of course there are many many more stallions and taking a look at a stallion guide or handbook in your area will give you a better gauge of semen availability.
So whith a Donnerhall, you are starting with a very good line, it really depends on what you want to add to the horse. It is useful to know what the crosses generally produce, so google and youtube are your friend. If you know of a breeder with experience in the lines you are looking at, then talk to them about their general findings with each cross. List your three top traits and breed for those, everything else is a bonus and with luck and a good cross you can end up with an athletic, ridable, sound horse with a good temparment and movement.
PS - these are just my personal experiences and opinions of these horses. I have my own biases and tend to place rideability over many other traits. Other people may have different opinions.
They say money doesn't buy happiness -- well happiness doesn't buy horses!