Well if I boot up 4 VM's on my Vista machine I run out of memory and thats just having 3 running with no programs running (uses 7.4GB) and then booting the last one. So I would say 12GB would be justified.
I personally wouldn't get a extreme chip since even though they are faster they're not really worth the extra cost.
And I'm American and I always send in my MIR
Money back is almost like free money though if you can get the intial costs to be lower by getting something with a MIR then I can understand..