Tjohn is absolutely right, it won't make any difference in the end. Patience is the key! I also agree with Rayraz, bulding a separate box completely will help you render much faster in Bryce than any sole upgrade. Also in 3DS, for certain! And, if you're going to actually spend $2k, you could probably build at LEAST three good machines. If not Five! That would effectively reduce your render times by 5, but also will cost you a lot in patience and upkeep!