If you want to shoot suppressed, the first thing you may notice is that your sights are probably blocked by the round can sitting at the end of your barrel. There are certain guns which are designed to be used with a suppressor and therefore come with taller sights to eliminate this problem.

It is really that big of a problem? Well not really, if you can deal with "shooting through the can" then more power to you. I personally feel that I cannot shoot accurately unless I am able to line up my sight posts. If you are going to add a suppressor to a run of the mill gun like a Glock by simply adding a threaded barrel you may want to consider having the sights swapped out for a set of "tactical" ones.

The image below shows 3 guns with an AAC Tirant-45 installed.
The first gun is a standard USP compact with a threaded barrel. It does not have tactical sights and while the photo didn't focus well on the front of the gun, you can see the sight picture is blocked by the top of the suppressor.

The middle gun is a Mark 23 which was designed to be run with a suppressor. As seen from the rear it does in fact have raised sights and provides the best sight picture (of these 3) in my opinion. The sight radius is longer than the other guns which allows for just enough light on each side of the front sight post.

Last is the USP-SD with a night sight front post. It does come with tactical sights which as you can see also provide a great sight picture. My only compliant with the tactical sights is the lack of dots on the rear post like the other two guns. The absence of rear dots makes target acquisition very difficult and sometimes even impossible in low light/dark shooting.