Well, if you can look for some HD5750 reviews, you can compare your performance @19" (1440x900? 1280x 720? 1280x1024?) with the closest resolution matching yours. Then calculate the percentage difference. If you find a benchmark @ FullHD (1920x1080) you can (+/-) add the percentage to their's and get a rough figure.
Unless if you find the exact benchmark with the exact setup as yours.