My 600w inverter runs my sat and older tv just fine, but some of the newer tv's degouse on start up and can be hard on the lower wattage units. The best way to power the inverter is with heavy ( maybe #6) power leads direct from the battery. If your trying to use the cigarette lighter plug, its not going to work well. And you will probably have to replace the inverters often.
You can find the best deals on inverters at truck stops. Flying J is the best. CW is kind of expensive for them.