First of all (this is a HUUUGE pet peeve of mine) if the horse is not branded and registered as a Hanoverian, it is not a Hanoverian, it is a warmblood. If both of it's parents are not in the studbook and it is not eligible for registration with the Hanoverian Verband, then it may have eligibility for registration with the American Warmbloods, Canadian Warmbloods etc..
I love Hanoverians. My first real dressage horse was a branded Hanoverian mare in the main studbook by Akzent and out of a Bolero mare. I competed FEI Junior Young Riders on an A-line gelding as well. I also showed a warmblood mare with Hanoverian ancestry, by Grande out of a Wenderkreis mare. And my current horse is sired by the Hanoverian Rotspon by Rubenstein.
They are wonderful horses - but you do have to watch out for some of the lines. Some have not been modernized - or poorly managed, and quite a few are known to have "personality issues" (aka the horses enjoy pitching people into walls - or rafters). Know what you are buying - research research research! And if the price is "too good to be true", then it probably is. Most broke, branded and registered major types of warmblood horses (Hano, KWPN, SWB, DWB, Westf. Etc..) start around $20,000. Generally anything less than that indicates unsoundness of the mind or the body.
I also am not a TB person. They don't like me and I don't like them. I have cracked ribs, a bruised lung, a broken foot and other bruised limbs strictly from those horses. I don't deal well with flightyness apparently