Photoshop CC and Smart Sharpen
The most recent release of Photoshop CC included a speedup to the Smart Sharpen feature. It now takes advantage of OpenCL which, if supported by your graphics card, can improve execution time via massive parallelization.
AMD posted an interesting presentation in November, 2013. Timings were based on a pre-release version of Photoshop. Slide 20 compares the time to Smart Sharpen an image using Intel's HD 4000 graphics integrated (free) in an i7-3770k processor with the AMD Radeon 7970 high-end graphics card ($450). At Radius 64 we have:
AMD: 4 seconds
i7-3770k: 45 seconds
Now that we have the latest release of Photoshop I thought I'd give it a go with an Asus GeForce GTX 650 Ti graphics card ($150 and a few notches below the 7970) running with an i7-2600k processor (a few notches below the i7-3770k).
To duplicate the results in the AMD presentation I used a 5616x3744 image and Smart Sharpen parameters Amount:500 and Radius:64.
AMD: 4 secs (from presentation)
GeForce: 4 secs (measured)
Whether you go with AMD or GeForce you will be well served.
My processor, the i7-2600k, does not support OpenCL. If you have a more recent processor with integrated graphics perhaps you could run this test and chime in. Be sure you've updated to the most recent driver and enable OpenCL in Photoshop's Preferences.