Inverters are not very efficient at changing DC Battery power to AC power. My 500W inverter can draw 40 amps of DC power when providing the rated 500W output. It needs to be close to the 12V battery source so you do not get a lot of voltage drop.
I too wanted to power my TV and DVD player with my inverter, but hooking it up and putting away was a pain with battery cables and extension cords and also then having to deal with them strewn all over.
I knew the inverter had to be close to the batteries, so I mounted it in the front storage area and used short heavy 8 gauge cables to run to the 12V to the tongue area.
I did not know where or how to interface to the individual AC outlet by the TV, so I decided to power the entire circuit at the Fuse/CB Box/Converter. The 15A CB that powers the AC outlet by the TV also powers the one under the Dinette table, the two by the bed and the second TV outlet in the bedroom. That's good, but the issue is it ALSO powers the converter. The hard part was isolating the circuit from the converter which it tied in right at the Circuit Breaker. I removed the length of 14/2 romex from the back of the converter and ran a short length of 14/2 in its place into a switch box that I mounted under the sink.
The 3-way switch allows the current in normal mode (up) to be routed from the Shore Power (or Generator) to the utility circuit and when switched down it routes the power from the inverter to power the utility circuit.
The AC output is routed down through the floor and frame cross-members with rubber grommets and cable clamps. It then goes back up through the floor into the trailer by the Fuse/CB Box/Converter under the stove and into the switch box.
When dry camping, I can access the inverter to turn it on and off by lifting the bed or by reaching into the storage area outside. Then of course I flip the switch to the Inverter position.
Maybe this post could be in modifications forum section.