The T-board does fit in the marker like Ninja said and is probably aside from a new barrel and possibly a better inline regulator the only thing you should need for the gun. The board itself comes with a lighter switch, comes stock with eyes to prevent chopping, and will help raise up your ROF dramatically.

Other than that I say the best possible upgrade would be a new marker when the time comes. Save the money you would use to build this marker and move up the ladder when you are ready.