A decent GPU will give you many more points per watt, but just not here at WCG - at least not yet, but soon enough. So, get the most energy efficient CPU for now (a Sandy Bridge) and worry about the GPU in the future; unless you especially want to crunch for an existing GPU project (GPUGrid, MilkyWay, Einstein...), all Boinc projects but with no connection to WCG.

Myelin computer modeling research has been carried out and published by several research groups, but I'm not aware of any Distributed Computing projects specific to demyelination, myelin atrophy or MS research.
This has been asked several times recently. DC tends to be large scale, so a DC project would have to be broad ranging.
You would probably be talking about using a database of known structures and analyzing their binding potential to proteins known to be important in the generation or maintenance of myelin, building a binding affinity database of interesting molecules to study further.

About my previous post, I was thinking in something like this:
http://www.gpugrid.net/forum_thread.php?id=2203#17646

Just some food for thought. My suggestion is based on no OC but expandability. I had at most 5 systems crunching at one time during my time at WCG. Fun but time consuming. Am on my fourth build after selling two dual processor systems. Decided I want just two but with as many cores as possible. With two, if one goes down, your still crunching until it's fixed. Found out the hard way when I screwed up a bios update. If your not planning on OCing, my suggestion is get a dual socket motherboard. Start with one processor, or fill both if you can afford it. Make sure you have at least one PCI E slot for a nice GPU to crunch a GPU project if/when they come available for WCG. Or if you want to try some of the other projects that do use GPU's.
For single processor systems, sandy bridge is the way to go. I prefer the west mere xeon processors, quad or hex. Not real cheap depending on the speed you want.
As for OS, I run dual boot ubuntu 64 and win7. Some projects have in the past run on one OS. This way I can switch when needed.
The cheapest hex xeon at new egg is just under 600 for a 2.4ghz. Two of these will get you 12 cores/24 threads. May not be the speediest but can get allot of wu's crunched with one box. You can change out later with bigger ones as the prices drop since the newer xeons are coming out in the near future.
Again, no OCing with my suggestions. There is a motherboard that will let you OC a dual processor setup. That is a EVGA board. You would have to ask folks who have this setup how it's working out as I don't use this board.
Allot depends on how much you want to get into crunching, electricity usage, etc. Plenty of folks here with different setups to ask questions. Good luck on your decision and crunch on.

Open a terminal window and type more /proc/cpuinfo
That should give you your processor speed.

Not exactly true.
Running Linux, the earned credit for a WU is less than running Windows. But ... since the host will compute more WUs under Linux than under Windows, the same host will earn more credit, even if the "more" is not "many".
Yves