Hi SMCK,
As you probably know from your reading here … the Serta Vantage certainly wouldn’t be an option I would consider and the lower quality materials would likely be an even bigger durability issue with your weight (see post #2 here). I would be very cautious here.
I would also make sure you can find out the information listed here about the Heggedal so you can make more meaningful comparisons with other mattresses as well. It wouldn’t have any obvious weaknesses like the Vantage but once again with your weight and the lower coil count pocket coil it may also not make the best possible choice either.
Phoenix