Remember 'Barbaro'? A perfectly proportioned thoroughbred who convincingly won the Kentucky Derby a few years ago? After his tragic death on the race track, the owners frequently repeated the mating, i.e. same sire and dam, with the hopes of creating another superstar horse. It never happened. Genetics are powerful, but creating a champion is rare and involves random luck.
This is what I think of when I see people spend a lot money, finding the right dam for their seed, hoping to produce superior quality offspring. Sorry, it doesn't work that way.