I agree; DPDT would work for the 300/600. Also, when I had the 633-UB16KKW015CCC-RO in the K250 I was repairing, I measured 2.2 volts across the LED. While this is a bit higher than the spec rating of 1.85V and may shorten the expected life of the bulb (although I put the unit through several hours of burn-in), it is comfortably within the rating for the super-bright and should not require any extra resistors.