it really comes down to the current market price:
Socket A can still be competitive performance-wise, but they are pricy
today because they're getting scarce. 754 Athalons are almost as good as
939, and until recently they were a tad cheaper, but today the 939 is
cheaper, again due to availability and it's the current model rolling off
the lines in quantity. 754 is all Semperons nowadays. MB prices are
pretty stable, w/ 754 about $15 less than 939.
The Intel world is similar - socket 478 has gotten to be more expensive
than 775, even tho it's the older technology. Try and find a cool-running
Northwood core nowadays - big price premium.
It's surprising how the latest technology is in fact the cheapest too,
simply because that's where the supplies are.
>> Stay informed about: New AMD system