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I suspect what is happening is that you are viewing the sharpening in DPP at less than 100% zoom. The sharpening available in DPP is pretty basic and I suspect that the way DPP interpolates for screen viewing is even more crude. In other words, when you are viewing the image within DPP at less than 100% zoom, DPP is giving you an exagerated impression of the sharpening being applied.
If you haven't already, I suggest you compare the pre-convert and post-convert versions making sure you are comparing both at 100%. Viewing sharpening at 100% is usually the best technique anyway, since even in Photoshop the interpolation for screen is not completely perfect.
As I said earlier, I always found the sharpening in DPP to be pretty basic. The original sharpening was essentially USM with a Threshold of around 4 or 5. It would only sharpen fairly contrasty edges and apply no sharpening at all to textures and more subtle edges. It was pretty easy to over-sharpen and not really notice unless you were checking carefully at 100% zoom.
Then they added the complete USM method, which is really the same type of sharpening - just with more control.
If you normally go to CS6 anyway, I would recommend doing your sharpening there.