Hi,
I would still use the inverter that you have. I really do not use my built in 1500 watt Trace inverter / charger much, because my smaller inverters are much more energy efficient. I have a e-meter that measures the amperage going in and out very accurately. The Trace might be drawing 8 amps running the TV, VCR, and other things in the RV, then change to the 150 or 300 watt inverter plugged into a cigarette lighter, and it will drop the amps by about 3 amps. That big inverter will consume a lot of power just charging up those huge capacitors and such.
I ran the small inverter with factory installed #8 wire going up to my TV set.
The Trace is hooked up to 000 wire and 4 golf cart batteries.
You can buy reasonable priced solar panels for around $1 per rated watt here.
SunElec.comGood luck!
Fred.