Here's the info I have based on xbitlabs.com's tests on the real response time:
First of all, let's note the VX922, which supposedly has one of the lowest response times on the market right now:
VX922 - real response time of 5-10ms...
so, how about in the 20.1" 1600x1200? S-IPS.BenQ FP2091 20-30ms or more simply: 30ms S-IPS.BenQ FP2092 30-18ms or more simply: 30ms S-IPS. LCD2190UXi 10-28ms or more simply: 16/ 28ms TN.Samsung 203B 4-36ms or more simply: 22ms TN.Samsung 204B 10-30ms or more simply: 20ms PVA.Samsung 214T 15-25ms or more simply: 20+-ms S-IPS.Sony S205K 20-35ms or more simply: 30ms
Considering price, the 204B looks like the best choice in that resolution. However, if you might consider widescreen, there is an even better choice: AS-IPS.NEC 20WGX2 5-10ms 7-9
Notice that is has a response time closer to the VX922 and it has perhaps the best panel type on the market (S-IPS with glossy finish) for image editing.