The Asus VB198T has a maximum contrast ratio of 50000000:1. That's over two times the contrast ratio of a 20000000:1 LCD screen, which is the most frequently found contrast ratio. Flatpanel monitors of this spec and age dynamic contrast ratios range from Mega Contrast (worst) to 100000000:1 (best).
It may also be worth also looking at one of the other LCD screens that have a 50000000:1 dynamic contrast ratio currently available including cheaper PC monitors such as the VB198TL (£138.60), or the VB178D both from Asus.
If the contrast ratio of this LCD screen is not high enough for you then you might want to look at the Asus VX207NE (£65.98) (100000000:1) which is also cheaper.