>Al gave you some reasonings. 64 bit on 4 Gig seems a waste unless you need 64 bit OS for a specific app. I think most advice I got said 8 Gig because that seems to always be the jump after 4. 6 Gig sounds weird.
I have a 3-core processor. I just had to have it. Sounds like one of those engines with three cylinders. After ages of everything being 2**n, I now have something odd under the hood. And it works fine.