I've got fast prime fever!

If I had to pick just 1 fast prime, I'd go 35mm on full frame without doubt.

The 35 f/1.4 is exceptional, but I don't think it's different enough from your current prime to bust you out of your rut.

For a fast prime change up, I know you said you didn't want either, but the 85 and 135 are vastly different to anything you have now. If you haven't tried them once, you owe it to yourself I got the 135 despite owning the 70-200 II. I love using it.

A 16-35 lens will be a nice shock to your system, that's for sure. I don't use my f/4 that often, but when's it's called into action, I love the challenge it brings to my shooting process.

MatthewK wrote in post #18341713
The 35 f/1.4 is exceptional, but I don't think it's different enough from your current prime to bust you out of your rut.

This. Personally I'd just be happy with the 35f2. I know I am.

Look at the 135 if you really need something new. You might also consider used as you can find one for $700-750 most days.
Save your extra coin for you Italy trip.