It's awesome that Wizard moves so quickly on things like this. We had been discussing the market for higher impedance IEMs a while back, but I had no idea that he would have something ready to go so quickly. I guess when you work 7 days a week, long hours each day, and really know your stuff, you get a lot done.
I'l repeat to you guys what I originally said to Wizard: this is a great idea. It's probably not going to replace the 3.Ai and 4.Ai in terms of mass appeal, but certainly should gain traction with a decent sized subset of us. Lots of portable players (even the nicer ones - or especially the nicer ones aimed at audiophiles) have higher output Z - in the range of 10 to 30 ohms. Pairing those with a 4.A (25 ohm) will result in a less than adequate damping factor and likely muck up the finely tuned frequency response to some degree.
Then there's the added bonus of tube amps. A lot of tube amps have higher output Z as well, and are just not suited for use with most IEMs. Which is too bad because using a high end tube amp to drive a high quality in ear monitor can be a great thing. I use my Earproof Atom customs (70 ohm) with a variety of tube amps and it sounds remarkably good. But even so there are some tube amps, especially the OTL variety, that still don't work so well due to a 50 or 60 ohm output impedance (or higher). The Tzar 350 will be pretty much the only IEM on the market to work well with those amps - and since it's Heir Audio, they will likely sound brilliant in the process.