Will a GPU upgrade improve my performance?

Hi guys

Actualy im multiboxing 4 Diablo 3 characters with the smallest possible resolution and settings.
Sometimes the game is freezing and laging a bit, and windows is poping up a message that the graphic card driver got a error and had to reload ( but no other problems,. just a small 10second freeze )

Thats my actual hardware:
Intel I7-860 ( Mugen II )
MSI GTX 460 Cyclone 1GB
Asus P7P55D - Be quiet 500W
2 x 4GB DDR 3 (8gb)

Could a GPU Upgrade improve my performance significant?

Thanks guys

[MiRai]

You can monitor your hardware yourself with this:

http://isboxer.com/wiki/HOWTO:Tweak_you ... ottlenecks

Both the CPU and GPU are on the weaker side at this point, but only the monitoring software will give you a better idea which is hurting the most.