I see. I'm interested to see if a combination of sorts will result in a lower FG. Mine bottomed out at 1.000 with just brown sugar, though I used cotes des blanc yeast. We've got another batch that (save for the apple juice) is exactly the same as EdWort's original recipe. I'm anxious to do a side-by-side comparison - though I'll have to consider that one was brewed about a month later than the other.
A quick taste-test of my uncarbonated batch before bottling was excellent though!
As I mentioned, I used KV-1116 which is an almost fool-proof yeast that finishes wines and meads in the .990-.998 range reliably. Yeast will likely have more effect on this than sugar type. Calories in 100g of different types of sugar:
white table sugar: 396
brown sugar (sucrose with 3.5-6.5% molasses): 373
dextrose: 370
So, with respect to fermentability and potential gravity I believe dextrose and brown sugar are nearly indistinguishable.