Are you talking upgrading to a Socket 939 or to the 3700+ on Socket 754? If you're talking about going to the 3700+ on Socket 754, it's a waste. If you're going to Socket 939, get the 3200+ Venice, it will be as fast as your Socket 754 3400+.
Was looking to upgrade to a 939. Hoping for something faster than the 3400, but I wasn't sure if the performance increase of any of the newer cpus could justify the price atm. Assuming CPU cost + $100 for a new mb, was basically wondering whether I'd have to spend in the 600-700 range to get a noticeable performance increase or if I could be in the 300-400 range and still get a reasonable bump.
It is definitly NOT worth the extra money for so small increase of performance!!
You also have to consider upgrading your graphics adapter for PCI-X one.
I, for one would never do this!
In june, AMD is releasing new socket AM2 and only then it would be wise to upgrade. Socket 939 is soon obsolete. But then you will have to change your RAM for DDR-2.
So, my advice is... wait till late summer and then switch to 939 and some dual core processor (the prices will drop when AM2 socket is released). Performance wise socket 939 is good for a year or two at least.
Of course its your money and you're the one to make a decision