thanks everyone for the great tips and suggestions...
the 12 volt cable that is in the "entertainment cabinet" ( which I only call entertainment cabinet since it has the outlet for the TV and the switch for the antenna booster and that "darn" 12 volt cable ) is the same gauge as the cable that is connected to the 12 volt outlet.
I think I am going to buy this inverter http://www.amazon.com/AIMS-Watt-Pure-Power-Inverter/dp/B007KDDSXQ/ref=sr_1_fkmr0_2?ie=UTF8&qid=1389547832&sr=8-2-fkmr0&keywords=600WATT+PSW+AIMS as suggested by RoyB.
thanks again this forum has been very helpful for a rookie RVer like myself.