MacBook Pro MA895LL/A 15.4 max RAM memory capacity?

Hello all!

I'm not sure where on the forums this topic has been dealt with, so I hope someone can help.

I would like to max out my MBP RAM, but with a bit of research, there seems to be some conflict as to the maximum USABLE amount that can be installed. (4 vs. 6 GB)

I will probably upgrade to the new OS when it becomes available, if that should matter.

I am not entirely clear as to the memory limitations of my hardware, combined with the current OS I'm using (Snow Leopard, all updates)

Santa Rosa Core, Core 2 Duo....

Suggestions and opinions??

Thank you,

Dave