Keep in mind that in Colorado (with a few exceptions), you can run a battery operated water pump to create a slow water speed high banker (which works quite well with my Gold Cube) without any permits (unlike a gasoline powered rig). I run a 1000 or 1200 GPH pump off of a 55 amp hour mobility (Gell Cell, deep charge) battery - it will run it for 15 hours or more.
A lot of Colorado gold is quite fine (30 to 50 mesh). The Gold Cube will pick up 100 mesh gold (as long as you don't run the water too fast, and you pre-screen to 8 mesh). Most of the time the fine gold floats away unless you are running gear that will hang on to it. The ultra fine stuff is hard to separate from the same sized black sand, however capturing it is 80% of the battle.