Thanks for suggesting www.DonRowe.com, 800 367 3019. Kyle is very helpful. They do not have a Dimesions win12 300T in stock. So it would be a matter of ordering and waiting 2 - 3 weeks until they get it in stock. He says I need a Pure Sine Wave, and that the current inverter has a transfer switch.
The one option with 1000 watt and a transfer switch is to go w/ the Kisae SWXFR1210 but the size is larger 17 x 9 x 4.5 than what I currently have 13 x 6 x 3.25. I MIGHT be able to put the larger size in the cupboard but it would have to be sideways and displace other components that are there. I actually just remeasured and I think I could put the 17" on the bottom shelf with the plugs towards the front of the cabinet and put the other components like the DVD player on the top shelf as an option. It would definitely change the appearance, but is probably doable.
Amazon carries Kisae same size with transfer switch either 1000, 2000 or 3000 watt.
I have a call into Sensata, manufacturer of Dimensions, 651 653 7000, and am waiting for them to call me back.
My concerns are what would be the pros and cons of going with the Kisae other than totally reconfiguring the AV cupboard? How challenging will it be to change out the converter w/ transfer switch?... Which wattage should I order if the cost isn't all that different? I don't use all the stuff in the AV cabinet, but need to be able to sell the coach with what the next owners might prefer to have. Changing to a Kisae will definitely alter the appearance of the cabinet.