I have 2gb memory in my iMac. I hate when the spinning rainbow mousewheel appears and then my 20 inch iMac starts to lag and be unresponsive. Would upgrading to a 4gb memory make much of a difference, speed and performance wise, for my iMac? This is about a late 2006 model or so. I found RAM Memory Upgrade: Dell, Mac, Apple, HP, Compaq. USB drives, SSD at Crucial.com and they have a scanning feature for your computer and it recommended I upgrade to this 4gb memory chip, crucial.com. I'm thinking of getting the 4gb memory at the top of the list.
Should I get this?
Is this a reasonable price for this product?
Or is this not worth getting?
If not worth getting, then whats a better way to help make my iMac perform better and faster?

Thanks