Suntower, although your question is to DG, I will chime in here, as my needs are roughly between your current situation and DG's (one of the most advanced power users on the board).
For me, using the older MIR SE, 12 gigs would not allow for the loading of all needed instruments/articulation templates coupled with MIR SE (MIR Pro 2 would require more CPU power than I currently have). For a typical moderate sized template using full VSL library instruments, 24 gigs seems to be the standard norm (and is what I have). For power users, using virtually all of the full VSL collections (not to mention libraries made by other companies), 48 gigs can be needed (the new options available using SSD's may very possibly change that). When you start layering orchestra/chamber/solo strings with each other, that alone begins to eat up a great deal of RAM (depending on # of articulations loaded, etc.).
OTOH, for lighter uses (and where I started), all four of the Vienna SE libraries, will fit quite comfortably on a system with just 8 gigs of RAM, with an older Q9xxx CPU.
Also, if all you intend to do are smaller chamber type works, using only a few instruments, even with the full collections, 12 gigs may be enough.