Hey,
This is what I think, if you want go to tomshardware.com, anandtech.com (not sure if spelling is correct) or do a search in google for this CPU's
Now, what I have read is this, for now there is no 64-bit OS, except Linux distros. And windows 64 bit is to come out probably next year. But, if you want the lastest you might consider them.
But, honestly don't waste to much $$$$$ for something you will not use for the next year or so. Games, apps, and such I think won't be available for the next year or two. Why??? You'd need to recompile all software to be 64-bit. Also, at least for the AMD 64 either FX or not, new and better motherboards will sure to out soon. Read that some of the current mobos have some kind of type pf bug. But, try to go to tomshardware.com or check around here to see what i know about this CPU's.
Hope this helps some.
cyberkan