I have read through quite a bit of the ESP-950's thread, and the second link I've also seen. The only opinion inside of that thread is that of someone who said "It's been too long since I've had an ESP950 here so it's hard to comment on the difference."
I was hoping that other people inside this thread might know the actual difference (or at least a more recent listen to each one). I plan to ask the same question inside the ESP-950's thread as well.
If you own the SRS-2170 you can always upgrade the phones or the amp at a later date, and keep upgrading as funds allow.
I don't think you can easily do that with the ESP???