New install - basic question

Hi I am currently using amd64 2 core processor but now have the chance to use 
an intel quad 64 processor.
This might be a silly question but is it best to do a compltly new install?
If so which stage do I download from the following list:-
 
 alpha: iso stages 
 amd64: iso stages 
 arm: stages 
 hppa: stages 
 ia64: iso stages 
 ppc/ppc64: iso stages 
 s390/s390x: stages 
 sh: stages 
 sparc: iso stages 
 x86: iso stages

Which chost and cflags should I use?

Thanks for any help
paul
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