Learnging how to optimize your scene for shorter render times is just as important as optimizing the hardware. So for fastest renders, be sure to do both.
For scene optimization, you can use the render diagnoistics for some clues, but best is to first know what kinds of things need to be checked (read the maual).
Be aware of the optimize scene command. It's a great thing, but know what it's doing so you don't delete something accidently.
Some obvious things to set as low as can be while still maintaining a good image:
Tesselation Levels (Especially SubD. Defualt 4 is usually way more then needed)
Sampling levels in the render globals(there are many, each for different things)
Depthmap shadow map size(don't make it larger then needed) and reuse maps when you can
If ray tracing, don't use 10 bounces if you only need 2
There is a lot more to this, most of which you can find in the manual or come up with just thinking about it. PFX has it's own optimzations too.
On the OS end, defrag your drives often. Clear up memory and cpu resources when rendering(close the apps you don't need open).
Render from the command line and make use of render flags(all in the manual). Close maya when rendering from command line to save ram.
As for hardware, your set up is good. If after optimizing everything you find (in the task manager) that you are using more ram then you have, then consider adding more.
Chances are doing all these things ( optimization, not adding hardware) will cut your render time down a lot, maybe even in half or better.
By the way, the manual is just an F1 (or in help menu) away. Use it! 
As for your general hardware knowledge(is RDRAM cool or crap), here's some sites to learn more and follow the news.
www.anandtech.com
www.2cpu.com
www.tomshardware.com
www.3dgpu.com
there are tons more, those are just ones I visit often.
Good luck and happy renders
~Garret
