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Fortunately, on Mac OS X you really don't need any additional software to shoot tethered with any RAW converter that can use a "watched folder" ... Which Lr can do.
Max OS X comes with a very handy, though mundane app that can handle getting images to your drive via tether and natively supports over twice as many cameras as Lr does. Also, Apple has been much more timely in adding tether support at the system level for new cameras, usually four to six months earlier than Adobe ... they add the tether support at the same time they add RAW support for new cameras ... Heck, even My old D70s is supported for tethering.
The app is called Image Capture and is in your Applications folder by default. It is simplistic and only offers one camera control, you can trigger the shutter and that's about it. Simply designate the folder you want Image Capture to save the images to, and set that as your watched folder in Lr.
If you are not experiencing much lag or stalls when Lr is rendering images already stored on your drive in your normal workflow, it is very likely more featured tethering software or even more RAM will speed up the process, no matter how much RAM you have or how powerful your processor is, the weak link is the throughput of the USB connection in getting the data to your drive in order for Lr to access that data ... Though, I would never discourage anyone from obtaining as much RAM as they can afford. More RAM is always more better ...