whetstone ,,,,,which one?

i just order a 240mm hiromoto AS gyuto(my first J knife),
and i want to buy whetstone to sharpen it,,,,
King 1000/6000(55$) or JCK Special Combination Whetstone 1000/4000(65$)?
if there is something else recommended in this price range?
Regards,
Uri

p.s: what is a Nagura Stone and do i need it?

Congratulations on your purchase, great choice!
Both King and JCK should serve you well.
I've had that combo JCK in the past and worked fine for me, nothing really amazing but it does its job.
King combo stone is often recommended here on KKF as a good starting point, so I believe either choice is good. Btw Amazon offers King combo stones for 38$ delivered, so you might want to check them.

Nagura is yet another stone that helps in creating slurry. I personally don't think that you need Nagura with those combo stones.