I also agree with you except if you need 11 channels, as Ken pointed out, the 4200 is not a comparison to the 1120. You need to go up to the X6300H, or the X7200W. I think the X7200W's price will drop like a rock in a year when the X7300W is out. The Anthem is really not a bang for the buck type and not a power house for sure, but some people are attracted by their ARC and perceived higher end quality.
By the way, my logic behind projecting the 6300's output (up to 7 channels driven only) potentially 10% higher than that of the 4200 is based on their power consumption specs, 750W for the 6300 vs 670W for the 4200. I must emphasize again, that you can't go by power consumption figures alone to project power output capability because we have no idea how each manufacture defines them. Based on published bench test data, there has been no consistent relationship. In this case I would be comfortably using power consumption specs for comparison only because I am comparing two current models (the 4200 is only a year older) made by the same company. Even then, I am talking about educated guess figures only.