I completely agree with getting more ram, but I don't undertand the position of getting more ram to use in a VM. If you allocate 4 GB of ram to a VM, that means you'll have a longer store/restore for that VM. If you only allocate 1 GB of ram to that VM, it's a much quicker store/restore. If a *real* computer runs out of ram, it then goes to virtual memory, which is typically much slower than ram. But in the case of a VM, when it runs out of "real" ram, the "virtual memory" is still real ram, since the then entire VM is running in computer memory -- including the virtual hard drive.Since you can get 32GB for about $170 why not just get the 32GB, like some one else said if you do any VM's it will help you greatly to have so much free ram to assign for the vm. Just use your iMac when you get it and if you feel it needs more RAM after the test then upgrade, if not you can just wait and ram will get cheaper over time.
Maybe I'm just not seeing it, but I don't see the benefit to allocating more of the Mac memory to the support of a VM with more memory. Maybe I'm just misunderstanding how it works, and if so, feel free to educate me.