Like most things, it helps to know what your budget is for a monitor. As for getting a monitor with a lower native resolution to fit a video card you currently own, I wouldn’t do it. A monitor is something that is normally kept for years and there are plenty of video cards that can handle 1680x1050 just fine for a low, low price. Also, video cards are like most computer items in that you can constantly get more capability for a cheap price. I would get the best and biggest monitor you can afford and let the video card issues, if you even have any, work themselves out over time.
As for monitors there are many to choose from and the prices are falling fast for them. I saw a 28" monitor at Newegg the other day for well under $400. You can get 24" monitors there for well under $300. I got an Envision 22" right before Thanksgiving for $145 shipped to my door. It works great. Shop around and you will find some really good deals on quality LCD monitors.