I heard somewhere that for audio apps, the core2duo is the best CPU so far, because the Corei series are not only more expensive, but add latency to audio due to their newer design. I don't know if this is true.
For anything else, like gaming, would you recommend a Corei3 over a Core2Duo (when using a moderate graphics card, like the Radeon HD 5750)?
More aboutcore2duo corei3 audio apps
i'd recommend the i3 for both (i3 is cheaper is some cases...)
I highly doubt that. In pretty much every app that is coded properly, a Core i3 owns a Core 2 Duo.
Whoever told you that is just plain wrong. A Core i3 in all apps will outperform a Core 2 Duo and a Core i5 will outperform a Core i3.