That looks like a lot of memory. Is your db server hosting more than the Orion NPM database? Are they VMs? Might want to look through Resource Monitor on your SQL server to find out how much memory it's using, and adjust accordingly. (I'm always suspicious of VMs with high memory requirements.)
One other trick to speed up Orion NPM is to remove all of the thwack and community elements from each page. Unless you find them useful, you're making calls to an external site everytime you load a page with those elements enabled. I always get rid of them (but don't worry, I have Thwack opened in a browser tab 
) and it does make a difference in page load times.