It can all be resumed in one word, respect.
I bought my SR80i for when i'm sitting at my computer, because i find that their lightweight and their flat pads are more comfortable to wear at the end of the day, when i remove my contact lenses and put my glasses back on. But ever since i've listened to them with the L-cush, it bugs me, because now, i know what i'm missing with the comfies.
Regarding the PS1Ks, you are so happy with your PS500, that the bar is set very high for the PS1K, so i hope that you won't be disapointed, i know i'm not.
Yessir...the PS1ks will truly have to impress, but I'm excited to give them the opportunity one of these days!