There is no such thing as the perfect monitor, and what is right for me might not be right for you. FWIW, I had a much tighter budget than you, and I bought a ASUS VS229H-P Black 21.5" from newegg.com. Besides cost, the main feature was it is an IPS monitor, which means the color rendition is better (I do a lot of amateur photography). It also has a HDMI port in addition to D-sub and DVI, so that I can plug my Rasberry Pi in at times or use it as a TV set hooked up to my DISH sat. system without a converter cable. I tend to think for me, monitors over 22" are too big, unless you sit further away from the computer than I do.
I should mention there is one thing I dislike about the ASUS monitor, and that is the stand is on the wobbly side. At some point, I will clamp it down to my monitor stand.
If you can't tell which monitor to get from the specifications and reviews, then the only thing to do is find a large electronics or computer store that carries the monitors you want to use, and look at them in person. Then buy the monitor from the store and salesperson that gave you the extra value of looking at in person, even if you could find the monitor cheaper elsewhere. If the store's markup is too high, then don't even go into the store to check out the monitor, just order online.