It'd be a compulsive (not impulsive) purchase. I truly love my LCD2.2's out of the Lyr with my Orange Globes. I just want to experience the spaciousness the HD800 offers, whereas the LCD's are a a bit more narrow/forward. I'm just quite worried about the sibilance and harshness I hear about all the time. Input appreciated!
There is an essential mod for the HD800 here.
There is an essential mod for the HE500 here
If you own the above cans, do those mods first. Then roll tubes.