Hard to come up with a hard and fast answer to this type of question. As
f0dder pointed out, a lot depends on which software you're going to use, how often you're going to use it, and how well it takes advantage of the hardware it's running on. A general rule of thumb is that most software is at least a year behind in using the capabilities of the silicone it runs on.
As of right now, it's my understanding that
Sandy Bridge beats out all comers for general PC computing use as far as "bang for the buck" is concerned. The i7-2600 models ($299-$329 street) stomp everything out there, and are more than adequate for handling anything you'll want to do on a desktop. The lower cost i5-2500 (<$275) edged out the AMD Phenom X6 in both CPU
mark and
value scores according to Pass Mark's metrics. Details on that
here.
Couple of good articles can be found
here and especially
here. From the look of things, the i5 and i7 both hit the sweet spot for a new 'power user' build. Normally I'd opt for the i5. That's because I always follow the old "
two or three chips down from the top-of-line" method for getting the best specs for the money when buying an Intel. But for something as central as a CPU, the $50 to $80 difference to go up to the i7 isn't enough to make me automatically rule out going for the higher priced chip. (Which is probably exactly what Intel was hoping most people would think when buying.
) I keep my desktops for an average of 4-5 years. So a little future-proofing isn't a bad idea when it comes to people like me.
The only problem is the
6-Series chipset issue which is being resolved as we speak. Intel has targeted the beginning of March as when the re-engineered chipsets will become available. They also announced a replacement program. Anybody that got a mobo with the problem part is eligible for a no-charge replacement despite the fact the problem (supposedly) will only effect about 5-15% of the chipsets out there. Nice to see a company is doing right by its customers for a change.