Do you find the TV does a more efficient job of supplying power to the cooler?
the dometic doesn't seem to strain our 4 banger diesel jetta electrical system at all. At a reasonable inside ambient temp the fridge probably isn't running over 15% of the time. The 550 will also run the dometic just fine even on hot days. We were in Death Valley last October and had no problems traveling with the fridge in the galley. It's just hard on the battery 'cause the fridge has to run so much. That's why I've switched to hauling it in the TV.
The old waeco manual has a chart that shows running times for different inside/outside temps. It also shows that it draws 6 amps when running but I've rarely seen it over 5 amps. I've put the page with that info below. You can find that manual on the web if you root around a bit.
One other thing - we put the straps on our fridge as recommended on the forum. They work great. We've never used the included handles.
We also carry a coleman cooler in our galley but we keep ice in it to cool beers, fruit etc. I also like ice in my whiskey.

r dickson