Any SIR will work. Put a low mount on the Reflex like the ARMS #15 or Trijicons own mount (RX15) and you should be able to cowitness without having to put the Reflex over the barrel with the bi-level. If you do get a bi-level, and mount over the barrel, you should get a slightly higher mount. The TAO1 will sit a little high on the SIR no matter what mount you use (Trijicons stock TA51 mount is the lowest by a small margin though). But its not too bad.

If you got the Troy system, you will want a different mount for the Reflex. Get the RX14 mount or the ARMS #15 mount with spacer... that will put the Reflex up to a level where you will be able to use it propperly.