Sub placement with just one sub is so crucial (read: difficult) because of room modes. Moving the sub location around moves the modes around but does nothing to alter the fact of having those same few mode areas. Modes being areas where the bass reinforces and sounds too loud.
The main reason you want to run your mains full range is because they also produce modes, just the same way as a sub. Only difference being the mains need to be positioned for stereo imaging. Still they add two bass locations so the sub makes a third. With low bass more is always better.
However good you get it with your speakers and one sub, if you want really exceptional bass then try adding a couple more. With four subs it hardly matters where they go, all the different modes average out, and the resulting bass is so smooth, articulate and deep you can hardly believe it.
The main reason you want to run your mains full range is because they also produce modes, just the same way as a sub. Only difference being the mains need to be positioned for stereo imaging. Still they add two bass locations so the sub makes a third. With low bass more is always better.
However good you get it with your speakers and one sub, if you want really exceptional bass then try adding a couple more. With four subs it hardly matters where they go, all the different modes average out, and the resulting bass is so smooth, articulate and deep you can hardly believe it.