ct1615 :
the 9500GT or ATI4650 would be a slightly better card and the ATI 4670 would also be a much better card, none need an external adapter.
The 9500gt performs nearly identical to the 8600gt.
Same amount of shaders and bus width with a 10Mhz core clock bump and a 100Mhz RAM clock reduction.
The only advantage it has is slightly lower power consumption.
A 4650, while quite a bit slower than a 4670, will still greatly outperform an 8600gt/9500gt and consumes even less power.
Both the 4650 and 4670 max out around 50w power consumption.