There can be a couple bottlenecks.
At Edit>catalog settings>file handling select the highest preview size, high quality, never discard. This is assuming you are using a 24" or larger monitor.
In catalog settings>Metadata deselect "Automatically write changes into XMP" You'll have to periodically force this as a matter of good housekeeping, on the files you are working on, to keep the XMP current with the catalog.
At Edit>Preferences>File handling set your Camera Raw Cache to 20GB. This is not the same as your previews, and 20GB is ample. You might consider selecting "purge cache" at this time.
Pre-building 1:1 previews can help a lot. More than anything else you can do. There is still some re-rendering in Develop, but the initial view is more accurate. For 60,000 images from 8 to 21 megapixel cameras, my preview cache is around 200GB.
You can choose this on import, or by selecting all photos in the catalog, then Library>previews>render 1:1 previews. It's fairly quick on import and you can start ranking and editing files while the previews are being generated, anyway. To re-generate ALL your photo previews can take hours, best to let it grind away while you are doing something else.
Re-optimize your catalog after.
Lightroom is far more CPU dependent than GPU. Additional memory benefits tail off rapidly after 8GB ram, unless you've got a dozen programs open at once, I'd guess. I typically only have Lightroom and CS6 running at the same time...