Intel Core 2 Duo E6400 2.13GHz (overclocked to 3.2GHz) with 2GB RAM here.

I used to have an old AMD Athlon 2500+, and I must say that the difference is great. I never get the feeling that I have to "wait" for a render to finish in Poser, it becomes more integrated into the working process.
In Vue, upgrading my computer meant the renderer time on a difficult scene would be a question of 0-2 hours instead of 0-10 hours. Cinebench 9.5 showed my new processor to be about 5 times as fast as my old, and yet the clock frequency is only about 60% higher.

Getting a multi-core processor is very advisable for anyone interested in renderering.