I have a dremmel with a router attachment...there is no way I would use it to slot for the t-molding, just routing the formica for the button hole on a couple buttons heated the thing up something fierce, I could only imagine what slot cutting all the MDF woulda done.
don't be cheap...buy the router, you'll never regret it...it's by far the most versitile tool I ever bought, you will find endless uses for the thing. besides for the price of the dremmel, the router attachment, and the bits...you coulda just bought a router...if you're doing an entire cab, I bet you burn out that little motor.