Collision Killing CPU/FPS/Performance - Suggestions?!

I am spawning a lot of cubes with 2D colliders on them. I have been putting in a lot of work to increase performance by basically turning of scripts that listen for collisions when not needed etc. As well as utilizing the physics matrix.

Despite this when I have one cube listening my FPS is dropping sometimes in the single digits when collision is taking place.

The problem is I want to be able to spawn like hundreds of cubes in an, besides this, an ultimately simple game. I am worried this might be game breaking.... any tips?

On a side note vSynce seems to be troublesome, any thoughts on this? I am making a basic 2D puzzle esque game...