With 16 cores what u get is ok.
http://en.wikipedia.org/wiki/Comparison_of_Nvidia_graphics_processing_units#GeForce_300_Series

It actually don't support opencl, even though says supports opencl 1.1
My card 9400GT has same specs & it mines only 2500 khash/s at 550MHZ & at 700MHz, mines at 3400 khash/s

So, it normal.
poclbm gives much higher rate in cuda than RPC.
Try poclbm.
http://bitcointalk.org/index.php?topic=1334.0