First, view the results at the CS5 Benchmark http://ppbm5.com/ to have an idea of where your computer will fit... and maybe even run the benchmark so you will know where it fits in the list
Second, a couple comments
An AMD cpu will never be as fast as Intel, due to missing firmware instructions
Unless you have a 10bit monitor and therefore NEED a Quaddro card, an nVidia GTX card is faster
Those export times of 150 - 180 minutes make a lot of sense, because it would mean that a fast Intel system would take about 30 - 40 minutes for the same task and that sounds reasonable.