I had one with the following upgrades: HDCD, upsampling, PS1000 power supply -- all I did myself (but none of which required any soldering), this one still works. The other had some upgrades -- yes, I think they were the half nelson -- that were done by the previous owner, but required soldering, and doesn't work. I've yet to diagnose this one, but it's probably pretty simple, as it did work for a while.