The only thing 64-bit is going to do is allow you to access more memory; there will not be a large speed increase.
I know some of you will disagree with me, but I bet if you check the numbers you will see that if it's faster, it's not by a whole lot.
64-bit SW is even released yet and won't be until the beginning of next year. So you will have to wait that long before 64-bit SW is released. 64-bit Systems and OS will not help you without having the CAD app running 64-bit as well.
You are going to have to have your users dumb down their models, or maybe the problem is in the way they are building them. Maybe their technique is not the way SW would require them to build it. If not then they maybe making a portion of the part with 3 features, but if they knew SW better they could make it in 1 feature. This would cut down on time too load the models. As for assemblies, maybe there are to many mates per part and this is causing slow times. Maybe there are in-contexted relationships this will cause slow downs. Maybe you have complex DT in the parts and assemblies, this will cause it to slow down as well. The incorrect Video card and drivers will cause slow downs.
I think most of your users problems are not with systems, but design intent and just the overall users ability to design using SW. Not saying they cannot design, just with SW you have to think different before the Design is started.
I am not sure if you have went through the FAQ's here or not so see below some FAQ's written:
faq559-871
faq559-1094
Regards,
Scott Baugh, CSWP
faq731-376