Hiding iCloud songs in iTunes?

Alright, so here's my issue. I have an iPod classic that I've been using over the years as a sort of hard drive for all of my music (160 GB... These things are awesome). I have around 2000 songs, which have been collected over the years from CDs, friends, iTunes purchases, etc. It's enabled for disk use, so I plugged it into my new Macbook Pro, used terminal to show the hidden ipod_control folder, and copied all the songs into iTunes using drag + drop.

Now, when I open iTunes, a lot of the songs have duplicates. Presumably, one of the duplicates is backed up through iCloud and the other isn't. What is the easiest solution to this problem? My natural response was to just delete all of the duplicates, but how do I know which one to delete? Can I hide the iCloud backed up songs? If I do that, will new songs purchased through iTunes still show up in my library? HELP! This is seriously the most annoying thing because I spent so much time going through and naming, organizing, etc. I have done a ton of research online and I haven't been able to find a solution to this particular problem. It looks like in iTunes 11, there was a way to hide iCloud songs, but there doesn't seem to be a checkbox for that in the iTunes 12 preferences.

So, I guess my main question boils down to this: How can I hide the iCloud songs in iTunes?