What you have is fine, i.e. as long your machine meets the system requirements of running Axure RP, you should be good. If you're experiencing performance issues with Axure RP, this is most likely from the amount of widgets/interactions you have on a page/s in your file. While this isn't a hard rule, we generally recommend keeping the widget count on a single page to no more than 500 widgets, 40 dynamic panels (and 100 panel states), and 1-2 repeaters. And while you can surpass this amount, you may run into some performance hits, both in the Axure RP tool and in the browser.
To speed up the performance, it may help to split up your heavy-content pages into several, smaller pages, and then dynamically link them together where it makes sense for your project. If you have any large images, try optimizing them via right-click > "Optimize Image". If you have any unnecessary dynamic panels (no special need for the widgets to be encompassed in a DP container), it'll help to break away the DP and group them instead. If you're working with adaptive views, make sure there aren't any unplaced widgets in all of your views, as this means they are not being used in any view, and thus, is safe to delete them. If you'd like some more targeted assistance in speedying up your file, you can email that over to email@example.com, and we'll see what we can do.
Last, Axure RP is still 32-bit on Windows so it wouldn't be able to use all of your 16GB of RAM.