Perhaps the zx300 and wm1a were on different FRs than what I'm using. I'm on 3.01 on the 1A and 2.01 on the zx.
They're may be some slight clarity differences that I'm missing because I'm 31 and my ears aren't as good as in my younger years, but the difference for me is not stark whatsoever. I own both and have no reason to say other than that I really hear. Sometimes I think I can hear differences, but then I go back and forth and I'm not sure.
If the difference is there, it's far less pronounced than you're making it sound like, at least on the firmware versions I'm using. I've listened to both with an Andromeda S, Rhapsodio Solar, and ZMF Eikon, all 3 very well regarded pieces of gear.
I will leave room for error because I don't know how good my ears are, but I remain firm otherwise and wish someone else can listen to see if I'm crazy, preferably someone else that owns both because IMO, a quick stop in a shop isn't enough to give you a good picture.
Before you spend The money, be sure that both players are updated to the newest FRB and listen again .
The last thing I wanted to say is that I bought the zx300 expecting it to have an inferior sound to the wm1a. It was supposed to be a companion device for the gym and snowboarding and such. now that I'm seeing that there isn't much of a difference it might be a replacement. I'm going to give it more time, but I'm not anticipating huge changes in my opinion .