Poser 7 can't use more than 4 cores, so an i7 won't help. A Q8xxx will be just as fast at a lower cost.
I'd suggest installing 8 GB of RAM right away, plus a 64 bit OS, preferably Windows 7. Windows XP 64 bit is also a good choice, but I'd advise to avoid Vista.

A fast graphics card is very useful for scene manipulation and preview, but Firefly (like almost all render engines) renders on the CPU, not the graphics card, so a fast graphics card won't help one iota during the production render.

You don't need that much RAM on your graphics card for Poser. 512 MB is more than enough.

You could consider a Velociraptor hard disk for your operating system and program files, plus a nice big secondary drive for your runtime libraries (Samsung Spinpoint F series, 750 GB or 1 TB, 7200RPM are fast, reliable and affordable). Spreading the load over multiple disks won't let you render at higher quality settings, but it will let you render faster.

Also consider upgrading to Poser Pro Base. The FireFly version of PoserPro Base is a true 64 bit application and can use far more than 4 GB of RAM (128 GB, as far as I know). That's where the extra RAM kicks in. You don't actually NEED it - a large page file can also cover Poser's need for memory, but those extra gigabytes mean that a large complicated render at high quality has a good chance to finish before you run out of patience.

Poser 7 FireFly is limited to 3 GB under a 32 bit OS, and 4 GB under a 64 bit OS. And it's these memory limitations that prevent you from rendering large scenes at maximum quality.

Actually, upgrading to Poser Pro and running a 64 bit OS is the only way to render complicated scenes at high quality settings.

Last, but not least: that "quality" slider on the "automatic" page isn't all that useful. I always use the manual settings to get a good tradeoff between render speed, memory usage and render quality, and generally my settings are quite different from what the "automatic" settings provide.

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

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