The Ivy Bridge will be ~20% faster and similarly priced to the current SB, and compatible with an LGA 1155 MOBO. So buy cheapo SB now and replace if needed later. I do business applications all day, and any waiting is my or my staff's time lost.
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If that doesn't factor in then people aren't busy enough or they own the company
but still don't want $30~$40+ hour labor lost.
Just of kicks, 10 seconds x 30 times a day = 300 seconds / 60 = 5 minutes; reality it's closer to 15 minutes in typical day. 5 / 60 = 0.083 hours per day.
0.08 hour x 5 days x $30 / hour = $12 / week
$12 / week x 50 weeks = $600 / year
$600 / year x 3.5 years (typical upgrade) = $2,100 loss during the life of the PC
The i5 will save you say the 10 seconds and the cost difference was $45. So unless there's some Russian math where $45 = $2,100 maybe you need to reevaluate your time. The best single upgrade that's the most cost effective to time is the addition of an SSD to any system: Servers {IOPS}, Workstation {typically Rendering}, PC in business, etc - time is money. I get people screw around and waste time all day, but since there's pattern or limit this evaluation simply adds needless wasted time. In fact as the speed and response, lag, diminishes I've found reduced waiting time actually increases attentiveness and further reduces wasted time.
Example, you place a request - if you have to wait during that time your mind wonders around {attention span}, but if the request and response time is minimized so does the mind wondering - productivity goes up. 10% of the population is in some form ADHD. Google and most businesses already know this...
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Bottom-line, it makes no difference to me what you get I'm sure it'll be an improvement.