Would be worth to upgrade the AMD Athlon X2 4600+ to AMD Athlon X2 6000+ ?  
 
The CPU fan(4 years old) I have will soon need to replace(going to get ZALMAN CNPS9700 LED 110mm 2 Ball CPU Cooler), and if I'm going to this I might found it worth upgrading the processor. I'm upgrading the memory from 2gb to 4gb in preparing to change over Vista X64.
 
I have the ASUS M2N32-SLI with 16.03 BIOS version.  
 
Thanks for any opinions you might have.

You're better off buying an AMD Athlon X2 5000+ Black Edition.  It comes with an unlocked multiplier, which you can then adjust upward and easily overclock it to the speed of a 6000+.  It's what I'm personally planning on doing; I currently have a 4200+.

That is right chedfz, good advice!
 
I self went from 5600+ to 5000 black edition.
It runs at easily 15*200..
http://www.tomshardware.com/2007/1 [...] page7.html

Except that the cache for the 6000 is double that of the 5000.  And if he doesn't want to overclock then the 6000 is a good choice.  But is $160 worth a 600mhz increase?  
 
FYI - I have a 6000 now and like it.