http://www.pcworld.com/reviews/sfchart/0,typid,10,00.asp

There is a good start for some reading on which are good and why. DVI-I output is a digital output. You may as well get it, although your current card is only outputting analog you may end up with a graphics card in the future that will make use of DVI-I output.

For LCD the important stats are:

Contrast ratio: you'll see numbers like 500:1 or 600:1 or 700:1, the higher the better.
Refresh rate: for example 8ms is great, 16ms is OK, more is risky if you are a gamer.
Brightness: 250 cd/m2, 300 cd/m2, etc.

The thing about LCD monitors though, is that most of the guidelines for advertising the specs above are not strictly regulated. For LCD monitors, if at all possible it is always best to look at the picture yourself first hand before buying.