Ram upgrade questions for M2N32-SLI-WF AM2 Board

First off, apologies if this is a total noob question.....I'm just not totally sure what my options are here.

I have an Asus M2N32-SLI-WF AM2 board that currently has 2x1GB Corsair 533Mhz RAM installed. (I have 2 RAM slots free.) I am currently running Windows Vista Home Premium x64.

After reading today's THG article regarding RAM usage in Vista x64, I am convinced that more memory is going to make a big difference, as I use a lot of memory intensive programs in my daily computer usage.

My questions are:

1) Is it possible to put 2x2GB into the last two slots for a total of 6GB of memory, or do all RAM sticks have to be the same size?

2) Does my new memory have to be the same speed (533Mhz) or can I get faster stuff (only as fast as my board can handle, of course)?

3) If #1 and #2 are not possible, would I be better served to simply discard the current RAM in my system and purchase 4x2GB entirely new, given the current low pricing?

Thanks for any advice that you can give...I appreciate it

Thanks for the advice

I ended up going with 4x2GB of totally new RAM. Unfortunately, now the bios shows 8GB installed, but only 4GB available and I can't figure out why.

per the article, home premium should see it all. the memory controler is on the CPU, so mobo shouldn't matter. mayby a bios flash would help.