You have a load of 600W with the lamps, not counting the fan when it is on for that switch. You need to find a switch rated for what you have, which may not be easy. The switches are designed for lights attached to the fan itself, not externally mounted lamps, so the total Wattage available on a switch is unlikely to provide more capacity. Now, there's nothing preventing you from separating the light circuit entirely from that fan/light switch and adding one dedicated exclusively for the lamps. Most standard wall switches are rated at 15A. If you want a dimmer for the lights, you might want to get a 1000w dimmer since for space purposes, you may need to remove the heat sink tabs, which will derate it from the maximum, and should still meet the 600W capacity. If the wall electrical box is not big enough to add a switch, then you'll need to take the existing one out and put in a larger one. This may be beyond your capability. It should be easy for an electrician. Basically, in the electrical box, you'd find the wire that controls the lights. Take it off of the existing switch, then put it on one terminal of the new switch, then jumper power from the box to the other terminal of the switch. That's one example for a typical situation, which MAY NOT be what you have - as in many things, there is more than one way to make a connection, and we're not there to tell exactly what you have to tailor it to what is needed.