FX CPUs are the 'extreme edition' of the A64 line. They're the best tested chips from the best wafers of silicon from the best line (ok, you get the point 8) ). They also have the multiplier fully unlocked so you can select any multiplier from 1 to 100 (ok, not 100 but you get the point... :lol: ), AMD's nod to the 'enthusiast' market. Of course, they can, and do, charge for that.
X2's have 2 cores (effectively) identical to the A64's single core on each CPU. They go from 2.0 to 2.4ghz. (fastest A64 today is 2.4ghz, FX's go up to 2.8). Dual core makes the system more responsive when you're doing something that normally would have tied up a single core PC (or at least made it run slow because its busy) like applying photoshop filters, rendering a video, etc., a dual core will either do it faster (if the software is made for it) or at least allow you to switch over and do something else (play games, surf web pages) without the lag and slow response you'd get otherwise. You can even have lots of spyware, trojans & virii loaded on your computer and not notice it... :twisted:
For games, technology isn't there to take advantage of dual cores yet, so usually a faster clocked single core is faster in games. But the X2's are already as fast as their single-core counterparts (excepting the FX series of course).
Depending on what you do for business (spreadsheets & word processing, software development, video editing/rendering, etc.) a single core may be better, or a dual core.
Dual cores are reported to OC pretty well. Some say as well as single cores, some say not quite... but heck, a 3200+ Venice core can hit 2.7-2.8ghz easily, so if a 3800+ dual core (same starting clock - 2.0ghz) can't make 2.8, but it still gets 2.6...
Mike.