This one's minor but it's worth it - from memory the 740B has both a digital and an analogue input. The picture quality will be better on the digital - however a lot of older video cards don't have a DVI output. It won't be a major improvement but if your wife doesn't play games she won't need a expensive video card so you may want to think about upgrading that.

The difference is in how the signal goes. CRT's need an analogue signal to display, LCD's need a digital signal. Video cards output in digital, so the train goes something like this.

CRT

Video card --digital output-> digital to analogue convertor --analogue output-> display

LCD (Analogue input)

Video card --digital output-> digital to analogue convertor --analogue output-> monitors analogue to digital convertor --reconverted digital output-> display

LCD (Digital input)

Video card --digital output-> display

The elimination of the conversion steps stops a loss of quality on each conversion. Also a digital input means that things such as adjusting monitor boundaries can be automatically carried out without the monitor having to approximate (which they are admittedly now good at).

The quality loss is not huge, but I've had two identical LCD monitors side by side one on analogue, one on digital and the digital one is definately sharper.