In my own revolver/micro x car, it's geared fairly low at 51.4:1 (11/58 pinion/spur, 2.6 trans, 3.75 rear diff, 2.92 front) and is my primary crawler these days (used more like a 2.2s than a scale/trail truck.) Castle says the micro x is fine for an 8lb crawler or scaler, but I'd agree that the micro x is too small (30 amp?) if you're gonna be running at full load all the time. The revolver is rated at 400w, so divided by 11.1, it should be capable of pulling 36a continuous. On 2s, your amp draw for the same work/wattage is going to shoot up to 54 and the esc is really going to suffer. My thought is that if you run 3s, err on the low/slow side of gearing, watch your temps (mostly the esc), and don't drive like a knucklehead full-time, it will work well.
In this application, I think I'd rather have the micro x than the sw4, just for the aux function. If you think you'll need more esc, such as running in a 2 speed car, I'd sooner recommend the mamba x (which I believe is also 60a, as well as the sw4?) so that you could run it on 4s instead, and have a functional built in bec (both the micro x and sw4 will need an external bec, unless you're planning to run your super sweet NOS hitec 645 that you still have from 20-some years ago.) Geared for the same top speed, more volts equals less amps. Less amps equals less heat. Do it to it.