Definitely set up the PC version!

When working with your collection, the difference between using the PC version and the iOS version is like having a whole toolbox or just a screwdriver.

The way to tell movies that you have watched from those that you haven't is by the Watched Date. So you'll want to set a watched date - even though it will be a ficticious one - for the movies you have already watched.

I'm sure there are many ways to do it, but here is how I would do it:
1. Transfer your collection from iOS to the PC
2. Create a tag, let's call it "Unwatched"
3. Flag all profiles (Ctrl-A)
4. Select Collection/Flagged/Set Tags from the menu, and set the "Unwatched" tag.
5. Enter all your previously watched titles.
6. Filter your collection on all not having the "Unwatched" tag.
7. Flag all selected (Ctrl-A)
8. Select Collection/Flagged/Last Watched and set your ficticious watched date.
9. Clear the filter.
10. Synchronize your collection with the iOS Profiler. Done

You can now delete the "Unwatched" tag, because you won't need it. In PC Profiler you can select unwatched titles by using Personal/Watched Status/Not Watched in the filters window, or in iOS Last Watched/Never.

If I had to enter 600 titles, I would probably invest in a cheap barcode scanner, so I could enter them easily in the PC Profiler, rather than adding them manually or adding them in iOS using barcode scanning via iPhone/iPad.

iOS Profiler is great for keeping track of what movies you have, and also flagging them watched when you do watch them. But I don't like it for entering titles. Your mileage may vary ...