I'd go with a 1066FSB CPU for that system, IE T9500, T9300. The 9400 is only an 800FSB, so would not have as much memory bandwidth.
Now you have it backwards. The T9400 and T9600 are the 1066FSB parts, whereas the T9300 and T9500 are the 800FSB's. Man we are on fire in this thread!
But yes, the T9400 would be a good alternative if it is cheaper than the T9500.