I have them... tbh not a huge fan even though on paper (overall signature, form factor, cable) it's pretty close to an ideal iem for me- but I guess you will find out for your own preferences
I still need to try a filter mod someone on the 4001 thread suggested.
Haven't actually listened to either of them in a while though (IEM use way down in recent months for the most obvious reason in the world)- I think I find the ex1000 the better IEM still, mainly for mid-treble balance & presentation reasons (even though this is probably the tricky area of ex1000 too, just a different type of problem that doesn't bother my ears so often). Actually think the 2000J makes a closer match (also had a mid-treble thing going on butof a more similar nature to 1000's), but the bass of all three exhibit some common qualities.
Look forward to another opinion on the 4001 though, not a lot out there (kind of flew under the radar I think due to price & people seeming to prefer the 3001).