I too have a large library (600 gigs in a range of bit rates, but 110k+ tracks) Also on a pretty fast i5 with 8gigs of RAM, with my library on a USB 3.0 drive.
I'm in the middle of rebuilding my library (moving machines), and it is painfully slow. But I tried the trick of putting it in "Now playing" view rather than Grid view - and it's blazingly faster. Makes simple sense, just never through to try it. I assumed the lag was physically copying files to the new library location and adding to the database, but apparently re-populating the grid view was a big part of it. Wow.
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