Although I really like the Z-4000, I'm loath to recommend them at this time. There are no parts available for them and they have been discontinued. Given the fact that the main circuit board is a lot more complicated in this transformer than most, and the unavailability of either service information or parts, I'd consider the other options.
I've hard all the comments about "My Z-4000 has run for years and never needed anything." That's all great and nice history. However, going forward, do you really want a $400 doorstop if it does fail?