Your picture is a little confusing, but I gather it's just a TM751 or RR501 plugged into an Appliance module with the necessary spacers for clearance. BTW, there's a little adapter made by Leviton that's _sometimes_ carried at Lowe's which helps with a setup like this - a two-prong plug with a two-prong socket at right angles and with the correct orientation for the second module to hang in the normal upright position below the first, so you don't need to use a spacer. (I wish they made something similar for three-prong grounded plugs.)
But there's another addition you can make to your system: Get another TM751 and plug it into the same plugstrip as your setup. Into this TM751 you plug a large capacitor. Now when the appliance module in this TM751 is actuated by a remote, the capacitor acts a big signal-sucker on the line and inhibits any X10 signals from being sent or received by the other two modules (or probably anything else on the same branch circuit). So you then have a master switch. :-)