If you think the PS500 is a bit better than the T1, my guess is that the PS1000 - for you, at least - would be even better (when I say "better", I mean "more pleasant" not technically better/more neutral -- The T1 is clearly more technically advanced and more accurate/neutral).
I am truly starting to think that, me owning the HD800, the PS1000 would make a fine, "warmer" and "crisper", change.
Heck yeah, that's why I love pairing the T1s with a top end Grado...I really like having that variety in my sound signature. I'm really looking forward to hearing the PS1ks. My T1s will be a permanent part of my collection for sure, and if the PS1ks take me even further into Grado bliss, I'm going to be a happy camper. I can definitely see why you would like the contrast between something like the 1ks and your HD-800s. It's fantastic owning one flagship headphone, but when you can own two it's probably even more fun :)
EDIT: I totally agree with your point about the T1 being a superior headphone technically, as well. Although I prefer the sound signature of the PS500s slightly more than the T1s, the T1s are the better headphone from a technical standpoint.
Edited by Focker - 6/26/12 at 12:39pm