I'm planning on getting the mid-tier Mac Mini with 4G RAM and the duo core i7 processor. What do you think would be the most RAM that I should consider putting in it? Should I take out the one 4G card and put in two 8G cards instead or just bumping it up with another 4G card? I do a fair amount of media encoding and conversion while running word processors and downloading as well: all simultaneously. Don't really want to see much of the good ol' 'BeachBall'! :)
OWC says that you can put up to 16GB in it but apple specs says 8GB. My Mac Mini i7 (2.7GHz) w/4GB ram came with 2 2GB cards, not a single 4GB card. I am assuming yours will be the same. Thus, you cannot simply add a 4GB stick. Also, when purchasing ram you should do so in matched pairs. A matched pair will always perform much better than sticks purchased at random.
As for how much? Take a peek at at the benchmarking done by OWC: http://eshop.macsales.com/Reviews/Framework.cfm?page=/Benchmarks/CS5BenchmarkPag e-MacMini.html ... I am always a fan of getting as much memory as I feel comfortable in spending.