My setup is similar to Blackhearted's: 4 GB RAM, Dualcore AMD 64 bit CPU, etc. (soon to be replaced by Core 2-based Intel CPUs).

I think he makes a good point about the fact that although dualcore won't speed things up directly in Poser, it will make your system much more responsive when you're doing other things while rendering. I often work in Photoshop while Poser renders in the background. With a single-core/single CPU the Poser rendering would slow down the system.

Like someone else has already mentioned: The 2 GB limit is actually a limit of 32 bit Windows, not Poser itself (in practice, the limit is about 1.8 GB. The theoretical limit is 4 GB, but Windows reserves the other half for itself).  There are ways to tweak the setup for Windows, so that  programs can take advantage of up to 3 GB (the /3GB switch), but it's generally not recommended and the application has to support it. Although Poser works fine under 64 bit Windows, it still (of course) won't see more than 2 GB. We'll have to wait for 64 bit Poser to take advantage of 2 GB+.

However, having over 3 GB of RAM is still useful (when you run XP with the latest SPs, Windows reports 'only' 3 GB of system RAM, even though you've got 4 GB), because if you're a multitasker and work with several programs simultaneously, each program can fit into physical RAM and things will go smoother/faster since Windows doesn't have to swap to disk that much. Although 4 GB sounds comfortable, I often find myself pushing the memory limits, so I really look forward to the day when most of my memory-hungry applications have been ported over to 64 bit.