I would go with ram with better timing than you listed.  And definitely get a second physical drive. They are sooo cheap now! Also check out the Quadro FX or FireGL cards if you can afford it. If you're not into gaming that is.

I just build a new machine (all from newegg) last week around on the Asus P5N32E SLI PLUS board (1333mhz FSB) with the Intel Core 2 Extreme QX6850 Kentsfield 3.0GHz. 3gb of Crucial Ballistix DDR800 (4-4-4-12 2t) RAM. 2 WD Caviar SE16's @ 16mb cache 7200rpm sATA.  8800gts 640mb pcie card. XP pro of course. ;)

This beast renders like mad and chews up all games at max settings.

I haven't installed Bryce yet but I am not sure it would actually take advantage of a multi-threaded environment. I know the RAM will help but that's about it.