It looks like that RPG game doesn't run quite as well on AMD CPUs as it does on Intel CPUs.
It's looking like even the X3 440 would not help you anymore than your current CPU.
You can test turning down the graphics settings and see if that helps at all.
And test with the sound turned off to see what effect that has on performance.
Empire: Total War is primarily stressing the CPU according to a benchmark check
(click the chart to get the rest of the article and it's notes) http://img265.imageshack.us/img265/765/aempiretotalwarcpus1680.png