Just one more vote for the 1000. I love mine. Quiet as a church mouse and very frugal fuel usage. Great for power outages at home and my office as well.
For the info of other folks, some have reported that they like the 2000 better because it will produce more power before coming out of econo mode.
As to upgrading converter vs getting a battery charger, IMHO the charger is less expensive and more useful. I can carry my charger where ever in my truck, use it two campsites over to help someone and it won't go with the trailer when I sell it. Modern multi-stage chargers are also light-weight. YMMV!