I went with the NEC 1760v...running about $420 on pricegrabber. Has less then 20 ms (quoted as 16 ms) response time, and excellent colors. Reading the reviews, this was the best crossover for me between price and performance.
That being said, the first time I played some fast-moving games on it, I did notice a blur that wasn't present on my previous CRT (a flat screen 17" CRT). However, the display is much sharper, and I like the larger viewing area a lot.
Buy from store, this is one item i wouldn't get at ebay. Dead pixels is an issue with these monitors, so its worth testing the product first. Resonse time is your main requirement so yor options are limited, BenQ is one of the cheapest and probably a good monitor, but im a save the extra bit and get a Sony, because, its a Sony.