HPA-4 I believe is their upgraded version of the LA-4 with a headphone amp that is highly regarded.
The HPA4 and the LA4 sound the same on 2-channel. I have the HPA4 and owned the LA4.
@mybuddy I spent a bit of time at the SBAF web site (a very interesting audio site) looking into the Schitt gear. Seems the Schitt Mjolnir v3 preamp (no remote) that I also own is a huge hit over there. It is my 3rd best preamp, but folks seem to love it.