I think Millions uses the 320, he'll likely chime in.
I never used the pink brick but I know it comes in 3 flavors - soft (from JKI), medium I believe is the Iminishi and hard from Watanabe. Soft cuts faster and hard, of course, dishes less. All three are very popular for removing metal fast, though I understand the deep scratches it leaves calls for a 400 or really good medium stone to jump to. JKI also offers a 230 that though a little slower doesn't leave the deep scratches.
If you want a cheap stone that works well and easily jumps to any 1K in your progression the King 300K is decent. It would also go well with the pink brick.
If you really want to remove metal fast there is the Atoma 140. You don't want to get too close to the edge with it of course.