I don't know what breed you have or what health problems they might have, but with that much inbreeding, I would ask the breeders about that. Are you going to breed? If so, you want to know what genetic weaknesses will get passed on. There are a lot of "double-ups" in the pedigree which will assure that the very best qualities will be passed on. That's why there are so many champions in the line. However, the worst qualities will also be passed along. These qualities may be hidden, recessive health problems. If you're going to breed you'll want to avoid these, and if you want a pet, you don't want to have a cat get ill. I advise you to ask questions before you buy and continue asking for advice when you breed. It sounds as if these people are active and knowledgable. If they are honest, they will not take offense. If they take offense, buy elsewhere. A new breeder needs someone from whom she can learn.
I used to breed collies. I know of a breeding to produce double-ups of the champion female mother. This half-brother and half-sister produced a litter of beautiful collies with excellent show qualities, but the pick of the litter had a micro-thalmic eye-it was useless. The vet had to open it surgically for cosmetic purposes. That pup and one other had heart murmers which would drastically shorten their lives, and half the litter had umbilical hernias. Of course, half the litter was sold as pets with a complete report of their condition by the vet. That breeding should never have taken place. Line breeding-rather distant line-breeding- for good eyes and no hernias should have been undertaken. Both female and male were healthy and had good eyes, good hearts, and no hernias. These were recessive genes.