Hello ! running Watch Slingbox Plug-in on Safari on my Mac with the following carateristics :
15-inch, Early 2011
Processor 2 GHz Intel Core i7
Memory 8 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6490M 256 MB
Software OS X 10.9.1 (13B42)
I'm getting my CPU get busy over 103% by the Slingbox internet plug-in for Safari
I found a work around for now , I'm using rhe Flash version if it at the following address : http://slingplayer.slingbox.com/embedded/slingplayer.php
but isn't the same user exeriance as the main page watch.slingbox.com
The question is why your plug-in take so much resources?
Change the video from "Auto" quality to "Best" (essentially denying the plugin the ability to use "Best HD" quality). My experience is that the SlingPlayer plugin for OS X is very aggressive about using the CPU and the difference between "Best" and "Best HD" is negligible.
See the "quality" settings described here.