I'm not sure if this is the right forum for this question

I'm experiencing a lot of lag problems using Cubase

I have a AMD 64 4000+ 2.41Ghz
With 2GB of Corsair XMS RAM
I'm running a Firestudio Project

I turned up the Firecontrol buffer to 1024samples
and I'm still getting a lot of lag, I'm assuming that it is a VST
problem

Would it be a better option to buy new RAM or a processor?
...or maybe something else?

Thanks