Hello Dommech,
Glad to see you opened new interesting topic.
If you arrange those assets in your market watch and make a picture/screenshot of it showing the third column with the spread, we might compare the spreads, and if anyone(even me) has a broker with lower spreads, we will share it with you.
Now, keep in mind that you do not need to trade all the assets in one broker. When I see that some asset has a lower spread with another broker it worths for me trading it there.