DDR2 SDRAM 533MHz is the recommend Ram type
Maximum Graphics Card Power (W) 50 W
http://www.nvidia.com/object/product_geforce_9500gt_us.html
It really depends on the Amps than the Watts for a Power Supply Unit. I recommend a minimum 26 Amps.
Don't forget, you probaby have a CD/DVD Burner that also need some amps, the mainboard needs some amps, the CPU needs some amps. each HDD needs amps and so does external drives and ports. With a 400 Watt power supply ( any power supply), you don't get the whole 400 watts, you only get about 85% and 15% is grounded.