I'd run in 1600x1200 mode on a 19", but I'd really prefer to have 85Hz or more, anything lower than 75Hz isn't too good for the eyes. I'd go for the G400, it's only a little bit more and you'll enjoy the higher refresh rates.
I'm a huge fan of Sony monitors. All I can say is make sure you are completely happy with the monitor when you buy it, if not, return it. I'm not saying they have a huge defect rate, but once you get a great Sony you'll never turn back.
Yet another option would be to get a Samsung or Mitsubishi monitor. Mitsubishi's aren't that much less costly than Sony's, but Samsung has some great offerings and make completely gorgeious monitors. I have a 17" Sony and a friend has a 17" Samsung, I like his better yet mine is "higher quality". Just something to think about. Samsung's 900NF is a great monitor. The 900IFT is great if you're looking for a flat shadow mask solution.