hmm but 4650 has 64bit and 9500gt got 128bit, I guess these results are with 4650 128bit version !!!
brother don't look at these things
the gtx295 have 448 bit whereas the 580 have only 386bit whereas in performance there is a huge difference between both cards similarly .there is no value of bit in budget gpu's and in new gpus because bit is only use to transfer data and instructions and a budget card work well low bit rates.
the main thing is gpu is the technology and 4650 is 55nm techolology whereas 9500gt is 65nm moreover look at the shader processors 9500gt have 32 shaders and 4650 have 320. shader ,although there is a difference in ati and nvidia shader but difference is difference
also look at texture units ,texture fill ,pixel fill rate and memory bandwidth and also checkout benchmarks before purchasing the gpu .
hope it will clear all the confusions in you mind
and by above benchmarks and benchmarks over all internet you can see that 4650 is performing much better then a 9500gt