If you go for the Dell ST2220M or L, you will be sorry. You don't have to take my words for it but I have actually compared the display of the Dell ST2220 and the Benq G2222HDL side by side at a shop which had both on display and the Benq model's color reproduction and viewing angles are vastly superior. Dell's color look washed out, brightness levels and gamma are all whacked even at the best possible settings. According to the reviews it also has backlight bleeding but I couldn't confirm that at the shop for obvious reasons.
I find it funny how people keep recommending the Dell ST only because they bought it. C'mon man, have you even compared that Dell to any other monitor in the 8k range? Even Asus monitors can beat that Dell monitor hands down.
Note: I am not talking about the Dell P2211H model. Its Dell's professional series model and is obviously much better than any of the other choices mentioned here but its also quite expensive, around 11k I believe.