Last week, Apple started shipping the new 27-inch iMac based on Intel’s Core i5 and Core i7 processors, and various websites have posted benchmarking results for the 2.8GHz Core i7 iMac and 2.66GHz Core i5 iMac. Timon Royer’s blog has posted Geekbench 2 benchmark results for all four processor configurations available for iMac.

As you can see in the graph above the 3.06GHz lower-end iMac model scored the lowest, while both the Core i5 and Core i7 iMac models offered significant performance boost when compared to lower end iMac. In fact, 2.8GHz Core i7 iMac more than doubled the performance on Geekbench 2 benchmark in comparison to the base 27-inch model. For just $200 more, the Core i7 machine also offers 35 percent performance increase when compared to Core i5 iMac.

In one of the forum posts on MacRumors, PeterQVenkman has posted results of Cinebench release 10, which shows Core i7 based iMac scored 4164 on single core rendering and 15217 on multi core rendering. The iMac scored higher that the 2.93GHz quad core Mac Pro that was released earlier in 2009 and is priced $3,000.

Electronista has also posted benchmarking results of 2.66GHz Core i5 iMac in comparison with older 2.4GHz Core 2 Duo 24-inch iMac. The website used Cinebench, Xbench and GeekBench tools for testing. They concluded by saying “In the single-core tests, we found that the Core i5 iMac already scaled higher than the 10 percent increase in clock speed would suggest, though not in an extreme way. It’s when the full power of the system was unlocked, however, that the difference became dramatic. In many cases, we’ve seen 2.5 to over 3 times faster performance from the 27-inch model than a predecessor barely two years older. Not, surprisingly, graphics performance is also much higher as AMD’s Radeon cards have advanced just as much in the same period.”

We have added graphs of the Xbench and Geekbench tests done by Electronista below. The benchmarking results clearly show that if you bought the Core i5 or Core i7 iMacs you haven’t made a bad choice. And if you are planning to buy an iMac, you should definitely look at the Core i5 and i7 machines. The 2.66GHz Core i5 iMac is available on Amazon for $1950.