A 64 bit PC is HIGHLY recommended. Go for a quad core.

At this time, Intel is ahead of AMD, so I'd advise to go for an Intel CPU.
You've got two choices: the Socket 775 or the newers Socket 1366 CPUs (and mainboards).

The Q series of CPUs goes into Socket 775 mainboards. Most socket 775 mainboards can hold 8 GB max, some only 4 GB, a very few can hold 16 GB.. Machines based on a Qxxx are quite affordable, you can have one with a lot of disk, a powerful graphics card, 8 GB of RAM an a nice PSU/system case for less than $800.

The i7 series of CPUs goes into Socket 1366. Most Socket 1366 mainboards can hold 12 GB, some can hold 24 GB. It uses triple-channel DDR3, so you should install 3 memory modules at a time.
The cheapest i7 CPU is competitively priced, but the 1366 mainboards are still expensive - the price tag of an average 1366 board is 3 times as high as the price tag of an average 775 mainboard.
DDR3 RAM is still a tad more expensive than DDR2, but the differences are getting smaller.

FFRender64 and RAM: The Firefly renderer in Poser Pro is a true 64 bit application, which means it can use up to 128 GB of address space. I've been able to render scenes that took close to 8 GB during render: multiple figures with hires textures and strand based hair.

My scenes often grow to 200-300 MB, excluding texture maps, so those 150 MB should render just fine.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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