P4's are not not capable of being placed into a dual processor configuration last i heard, so choosing athlon over p4 is already decided for you if you plan to use a dual cpu system, the only other alternative is the xeon, which is a much more expensive configuration. The current p4 northwoods are indeed better than athlons by a good deal, but older p4 processors are easily matched by athlon equivalents, even though the clock speeds dont match up. It is quite true that dual cpu systems will rarely have a very significant effect on the overall speed of an application, but try running both photoshop and 3ds max at once, both smp compatible, with a single processor, and both at once with dual prcessors, and i guarantee you the difference will be as clear as day. As far as the mac guys, i have used a mac extensively in the past, and it is a great system. If you can have both, i highly recommend it. However, in this case, i believe a windows pc is better suited to his task. And i instantly tone out anyone whose only true case for choosing a mac over a pc is that individuals personal bias against "monopo$$oft" ,as those opinions are rarely argumentive or even informed. And both windows 2k and windows xp both run quite stabily on my system, a little fiddling is all that is needed. Which one you choose is often a matter of what other tasks you plan to use the system for, but for pure 3d apps and pure poser, i would recommend 2k over xp. XP is not a bad choice if you plan to do other things with your computer that windows 2k was never really meant to handle. If you do choose xp, make sure to get the pro version and not home. Final 2 cents, you can set cpu priority in the task manager for a dual processor system, and cpu "affinity" as well. If you have 2 processors and are running an application that only takes advantage of one ... tell that application to only use one and tell your other application to use only the second one. You will find that you can render full scenes in poser in the background and still use your computer as if you werent doing anything else on a similar configured one cpu pc.