Not sure about a tutorial (you might look here
, or at the Maxwell channel on youtube). That said, I'll mention first that wattage is meaningless without also specifying efficacy. However, probably more importantly, the camera in your scene is set up for a shot in broad daylight (EV=14). If you set up a similar scenario in real life, you'd be hard pressed to detect the spotlight, until it was nighttime, and you adjusted your camera EV to the 5-7 range. In that case, a single spotlight with 1100W @ efficacy ~50 would be very bright indeed.
Just try that as an experiment -- start with the environment & camera as they were in the file you sent (Env. Type=Sky, EV=14), start FIRE rendering, then set the Environment type to None, then adjust the camera EV to 6. While observing the effects of these actions, think about how it would work, were you shooting this in real life, with a real camera -- it is not possible to set the exposure to deal with the relatively-bright ambient lighting, and also to detect much light cast from fixtures in the room, simultaneously. Think of photographing the exterior of a house in broad daylight -- it doesn't much matter whether the lights are on or off inside, the windows will appear dark either way, which is why so much real estate photography depicts houses at dusk.