Hardware MPE does timeline rendering while editing in PPro http://blogs.adobe.com/premiereprotraining/2011/02/red-yellow-and-green-render-bars.html but does not, as far as I know, do anything to make Encore faster when creating a DVD or BluRay
Here is what I do that does take advantage of GPU MPE. My workflow is to export my AVCHD from Premiere to MPEG2-DVD and then import the timelines to Encore. Even if you are using no MPE accelerated effects and other features you are scaling from 1920 x 1080 to 720 x 480 for the DVD which is significantly accelerated by the GPU MPE in Premiere.
The Quadro 4000 is a lousy, expensive MPE GPU engine (only 256 cores), invesitigate using one of the current GTX 600 series, I know they can be made to work in you Mac if you have a current version OS and do not mind making a small text edit to one Adobe file. Search the Internet