I'm building a developer PC and am wondering whether to get 8GB or 12GB. It's a Core-i7 860 system, i.e., 1156 motherboards with 4 slots for RAM sticks, dual channel, usually up 16GB (as opposed to 1366 sockets where 6 banks / triple-channel are used).

8GB would be cheaper to get especially because price per GB is lower with 4x2GB compared to 2x4GB. Also the availability is worse for 4GB DIMMs here where I live; those are the main practical advantages of 8GB. (Edit: I should have stressed the price difference more - in the eshop I'm buying from, the difference between 12GB and 8GB is so big that I could almost buy a whole new netbook for it.)

However, I understand that more RAM can never do harm which is the point of this question - how much of a difference will 12GB make as opposed to 8GB? Honestly, I've always been on 3.2GB systems (4GB but 32bit system) and never felt much pain from having too little memory - of course there could be more but for instance compiler's performance was usually held back by slow I/O or not utilizing multiple cores on my CPU. Still, I'm not questioning that 8GB will be useful, however, I'm not sure about the additional 4GB difference between 8 and 12 gig. Anyone has experience with 8GB / 12GB systems?

The software I usually run all the time:

• Visual Studio or Eclipse (both should be fine with ~2GB RAM, after that I feel their performance is I/O bound)
• Firefox (it can never have enough RAM can it? :)
• Office (~500MB RAM should be enough)
• ... and then some smaller apps like Skype, other browsers, some background services etc.