I still need to acquire the 13,000 and possibly one of the lower grits 400 or 700. So you ended up with the 140 Atoma as well, I just have 400 and it works like a champ.
Steve, I only added the Atoma 140 after reading the concerns expressed about how hard the Sigma #400 could be on the Atoma #400. I tried using Silicone Carbide grit to flatten it, but it was a mess without a sink. It was also rusting my Veritas Lapping Plate (yes, I know you're not supposed to use it with water).
Because of my obsession with consistency, I try to eliminate as many variables as I can (my skill level gives me all the inconsistence I can handle). Since I am using an Atoma to flatten my #1200 and up stones, I wanted an Atoma to flatten the #400 stone as well. Consistent with his "non-salesman" ways, Stu suggested an iWood - at half the price. I did think about just sticking a #140 sheet onto the back of my Atoma #400 plate, but didn't think it was worth the $17 savings.
By the way, I have no problem going from the Sigma #400 to the Sigma #1200. I thought about the #700, but think that's really an overkill (even for me). The #13000 is probably also an overkill, but it produces a jaw dropping edge. The first blade I sharpened was my Lie-Nielsen 102. I always liked that plane, but never before knew what it was really capable of doing.