Will increasing my RAM change performance?

I have read online that increasing my RAM will not change my CPU usage being at a near constant 100% when running a java program/windows explorer window/browser simultaneously however I would like to know if it will be any different for a virtual machine. At the moment I only have 4GB on my iMac, 2.25GB (the max) has been assigned to my VM with 2 cores. I was wondering if I upgrade to 12GB (through 2x4GB RAM sticks) and assigning 6GB to each machine (Mac and Windows) this would help my VM's performance. If not, would I be able to assign 3 cores instead of 2 to my VM without the real slowness on both machines. Currently if I assign more than 2.25GB RAM or more than 2 cores, my computer basically freezes and is unresponsive, hopefully by adding more RAM to my computer I will be able to assign another core (or maybe all 4?) to my VM which will help with 100% CPU usage.

Is this a good idea and will it work, or will 12GB RAM split between Mac/Windows help on its own?

EDIT: I think it's important to tell you that I am running Windows 7 64-bit with only 2.25GB RAM, I read online a 64 bit system is useless without 4GB+ RAM, could this also explain why having 3+ programs on my VM spikes it to 100% CPU?

 

Considering no one has bothered or knows how to help me, I decided to my own experimentation. I bought the 2x4GB RAM sticks and my VM seems to run a lot smoother when I run using 6GB rather than 2GB. I do not see a need in assigning more cores because my VM's CPU usage has decreased considerably (whether this is because it is 64-bit or not I do not know), however is there a way to use all 4 cores simulatenously on both Mac and Windows for maximum efficiency via Parallels or not?