i downloaded luxrender today and rendered the basic monkey scene and immediately noticed an improvement compared to internal render. I then went to my current project to render it and after 5 mins of rendering my fan on my CPU was screaming and i was at 58 degrees Celsius. and combined with the noise of AMD fans, i panicked and stopped rendering.
So this is basically why im asking if you should use a hybrid of cpu and GPU or is CPU alone better.
I have an AMD Athlon II Quad Core 3GHZ