What version of OSX is right for me?

[ijhu]

Snow Leopard or Lion will runs fine with 4GB RAM. Not sure where you heard that Lion is RAM hog, but based on my experience, it isn't and relatively the same between 2 versions. Depending on what you are planning to do with your system whether it is just a normal day to day system or for other purpose. Your board has 4 slots and supports up to 8GB. You still have the upgrade option.

 

[ijhu]

Yes, 4GB RAM should be fine.

 

[Coupz]

Even on the MacBook Air 11 inch from my little sister (Core2Duo 1,4GHz, 2GB RAM), Lion is running smoothly