Novel single electron transistor (SET) read-out circuit designs are described. The circuits use a silicon SET interfaced to a CMOS voltage mode or current mode comparator to obtain a digital read-out of the state of the qubit. The design assumes standard submicron (0.35 um) CMOS SOI technology using room temperature SPICE models. Implications and uncertainties related to the temperature scaling of these models to 100mK operation are discussed. Using this technology, the simulations predict a read-out operation speed of approximately Ins and a power dissipation per cell as low as 2nW for single-shot read-out, which is a significant advantage over currently used radio frequency SET (RF-SET) approaches.