Xrumer host question.

Hello, can anyone please tell me what resource I should look for to increase the speed of xrumer posting ?

Is it internet speed, ram or cpu ?

I now have 8gb ram, quad core 2.85 ghz, 100 mbit, and it can post about 800 posts/min. So, what I need to increase, it seems it uses < 2 gb ram.So, what I need to increase posting ? internet speed ? should I get 2X quad core or should I only increase the internet speed.

Thanks