You can see many koi on
www.tviske.be where some are SFF koi.
For Kohaku I like a few parents a lot.
Beauty rose is very nice because of her bodyshape and growthpotential.
Ruby has a really superb skinquality but is more skinny than the others.
I also like Tsuke Tsuke Rose because of the body and the shape of the head, however, koi of this parentset are more difficult to grow to jumbokoi.
Very nice is Benibana, but the mother has passed away, jumped out of the pond, two years ago. Sakai still breeds with an offspring of Benibana called Benibana-daio, she has a nice quality, but not the same as the mother.
I hope this can help you a little