I have a 750Mhz with 256 ram and complex scenes like that take a long time on any machine were Bryce is concerned. I always try to cut corners when building a complex scene in Bryce seeing if I can do something in a way that wont extend rendering time but if its not possible you have to go the long way.

"But I being poor, have only my dreams. I place my dreams at your feet. Tread softly, because you tread on my dreams." --William Yeats